Biography

Early Life
Humberto Acosta-Rosario was born in Mayagüez, Puerto Rico, on January 15, 1947. His parents' names were Alfredo Acosta y Acosta and Carmen Rosario (maiden name) de Acosta (married name). Carmen’s last name indicates both her maiden name and her married name, a common practice in many Spanish-speaking countries. Humberto’s father worked as a factory laborer and later as a brewery worker.

Acosta-Rosario was active in his community prior to leaving for Vietnam. He loved sports, in particular, basketball. He also volunteered at a recreation center, coached baseball, and sponsored a local Cub Scout group.

Homefront
Mayagüez has always been important to Puerto Rico's economy, as the land there is very fertile, and many agricultural businesses are centered there. Textile businesses used to be in this area, including one that manufactured uniforms for U.S. soldiers. 

In Mayagüez, life was impoverished. The largest employer was the Bumble Bee Tuna cannery. This plant was established in 1962 and operated for 50 years before shutting down. In the 1960s, most of the population was native-born, and the median income was $1,341. Of the 21,111 households in the community, 12% did not have electricity, 40% lacked a septic tank, 71% did not own a car, and 65% lived in wooden-framed homes. The area was not as developed as the mainland of the United States or even certain parts of San Juan. Workers in Puerto Rico earned significantly less than workers on the United States mainland during the 1970s. The average Puerto Rican resident earned $1.60 per hour, while mainland workers earned $2.42 per hour. 

Mayagüez was home to the Asilo de Pobres, or the Municipal Poor Asylum, founded in the 1800s and operating into the 1970s. According to the National Register of Historic Places, the Municipal Poor Asylum was originally formed to help deal with the “problem of loose poor or mentally deranged people in the city.” The building itself also stands as an example of architectural achievement in Puerto Rico, showing specific elements of the Mayagüez Area.  

From the 1940s through the 1960s, the University of Puerto Rico expanded its Mayagüez campus to make college more accessible to citizens across the island. Their goal was to eliminate obstacles that prevented students from all backgrounds and neighborhoods from attending college. 

As the Vietnam War escalated, the attitude on campus changed to one of protest. Young men who were likely to be drafted began to protest and felt the pressure of the war at home. Like other students, they had to leave campus for basic training immediately. Private universities on the United States mainland had more room for protest, but the University of Puerto Rico at Mayagüez, which was solely dependent on federal funding, cracked down on student-led protests. 

Despite lacking voting representation in Congress (Puerto Ricans elect a representative who serves in Congress but does not have a vote), Puerto Ricans were eligible to be drafted into the Vietnam War.  Puerto Ricans made up only 1% of the U.S. population at this time, but comprised 3.5% of the soldiers drafted. 

In 1965, a young Puerto Rican man named Sixto Alvelo refused to be drafted. On August 6, 1966, Alvelo spoke at a rally in Times Square, New York City, attended by 25,000 people.

The 1960s and 1970s also saw an increasing debate over whether Puerto Rico should be an independent nation, a U.S. state, or a commonwealth. A plebiscito (plebicite or referendum), held on July 23, 1967, asked voters to choose among three political status options for Puerto Rico: Commonwealth (Estado Libre Asociado), Statehood (Estadidad), or Independence (Independencia). The majority of Puerto Ricans voted for a commonwealth status. 

The independence movement was often linked to the anti-war movement, and Reserve Officer Training Corps (ROTC) programs at universities were targeted for protest. Some were vandalized, and others faced bomb threats. Clashes continued between police and protesters, and the FBI investigated activities in Puerto Rico, including protests and flag burnings.

Military Experience
Humberto Acosta-Rosario graduated from high school and briefly attended college in San Germán, Puerto Rico, before being drafted into the U.S. Army. He was assigned as a machine gunner in Company B, 1st Battalion, 5th Infantry Regiment, 25th Infantry Division. He signed the induction paperwork on October 4, 1967.

Each company of about 150 men had eight M60 machine guns. The M60 was nicknamed “the pig” because of its size, weight, and the sound of the gun. The enemy greatly feared this weapon because of its firepower. The gun weighed 24 pounds and was 43.5 inches long. It was stabilized by two legs and could fire 550-650 rounds per minute.  Soldiers were told in training that machine gunners were the enemy’s targets and that the average machine gunner lasted only seven seconds in battle.

Acosta-Rosario deployed to Vietnam in March 1968. On August 22, 1968, his unit was stationed near the Ben Cui Rubber Plantation, owned by Michelin, a tire manufacturer. At 6:40 a.m., Company B departed Dau Tieng through an area of dense jungle. Shortly after 9:00 a.m., the group found North Vietnamese Army (NVA) hand grenades and web gear and came under heavy fire a few minutes later. The unit was forced to withdraw and called in airstrikes, artillery attacks, and helicopter support.

Once the company regrouped, they realized that two machine gunners were missing: Humberto Acosta-Rosario and Philip DiLorenzo, Jr. That afternoon, the unit returned to the area. DiLorenzo’s remains were recovered, and several wounded soldiers were evacuated for treatment. Acosta-Rosario’s remains were not found. 

Conflicting reports indicated that Acosta-Rosario may have been taken as a Prisoner of War, but those were never confirmed, and his status was never changed to reflect that. He was last seen wearing a white t-shirt, jungle fatigue pants, a steel helmet, and a gold watch.

Commemoration
Humberto Acosta-Rosario was officially declared dead on March 1, 1978. Of the eighteen Puerto Ricans listed as Missing in Action during the Vietnam War, he is the only one whose remains have not been recovered. 

Extensive searches were conducted looking for Acosta-Rosario’s remains. Investigators from the Joint Casualty Resolution Center (JCRC) conducted a search in August 1975. The investigation continued through the 1990s, interviewing local villagers and Vietnamese refugees, and searching for graves. In 1987, investigators followed leads from a source, but were unable to identify any remains from this information. 

Humberto Acosta-Rosario was posthumously promoted to the rank of staff sergeant. His name is engraved on panel 47 of the Vietnam Memorial in Washington, D.C., and is listed on the El Monumento de la Recordación (the Memorial Monument) in San Juan, Puerto Rico. His name is memorialized on Court B of the Courts of the Missing at the Honolulu Memorial at the National Memorial Cemetery of the Pacific in Honolulu, Hawai‘i. Ten days after he was officially declared dead, his father requested that a memorial marker be placed at the Puerto Rico National Cemetery in Bayamon, Puerto Rico. 

A recreation center in Mayagüez has been renamed in his honor.

More than 20 years after his disappearance, his brother, Alberto, marched in a Memorial Parade in New York City, still believing that his brother could be alive. 


This profile was researched by Ms. Jennifer Luneau, a teacher at Constitution High School, as part of National History Day’s Researching Silent Heroes program in the 2025/2026 academic year.

This profile was funded by a contract with the American Battle Monuments Commission.

Bibliography

Primary Sources
Alfredo Acosta and Carmen Rosario. Puerto Rico, Civil Registrations, 1885-2001. Digital images. Ancestry.

“Asilo de Pobres.” National Register of Historic Places Inventory Nomination Form. U.S. Department of the Interior, National Park Service, 1985.
Asilo de Pobres. Photograph. 1923. Fundación Luis Muñoz Marín (85003087). https://prahadigital.org/s/flmm/item?uid=cf1111df-2938-11ef-a756-0242ac190002. 

Atiles, Antonio. Supervisión de cosecha en una de las fincas del Colegio de Agricultura y Artes Mecánicas de Mayagüez. Photograph. 1955. University of Puerto Rico (1043020). https://upr.contentdm.oclc.org/digital/collection/ELM4068/id/1257/rec/10. 

Avilés-Santiago, Manuel G. “From Sugar Fields to Rice Fields: An Oral History of Puerto Ricans from the Vietnam War Generation.” Journal of Veterans Studies 10(1): 2024, 48–63. https://journal-veterans-studies.org/articles/10.21061/jvs.v10i1.303. 

Bigart, Homer. “Puerto Rican Nationalist Group and Carmichael Form Alliance.” The New York Times [New York, NY], January 27, 1967. https://www.nytimes.com/1967/01/27/archives/puerto-rican-nationalist-group-and-carmichael-form-alliance.html.

Brown Ramírez, Roy. “Monon.” Song lyrics. 1969. Vanguardia Disco Libre. https://genius.com/Roy-brown-ramirez-monon-lyrics.

Census Tracts: Mayaguez, P.R. Report. 1962. U.S. Census Bureau. https://censo.estadisticas.pr/sites/default/files/Decenal/USCB_CensusofPopulationandHousingPHC1-178CensusTractsMayaguez_1960.pdf.

“Humberto Acosta-Rosario. The Coffelt Database, December 2005 Update.” National Archives and Records Administration. https://aad.archives.gov/aad/record-detail.jsp?dt=1806&mtch=8615&cat=all&tf=F&q=B&bc=48&rpp=10&pg=9&rid=125&rlst=125.

“Humberto Acosta-Rosario. Combat Casualty Files, 6/8/1956-1/21/1998.” National Archives and Records Administration. https://aad.archives.gov/aad/record-detail.jsp?dt=197&mtch=1&cat=WR28&tf=F&q=acosta+rosario%2C+humberto&bc=,sl,sd&rpp=10&pg=1&rid=37995. 

Humberto Acosta-Rosario. Freedom of Information Act Response, including partial and redacted Official Military Personnel File and Individual Deceased Personnel File. National Archives and Records Administration - St. Louis. 

Humberto Acosta-Rosario. Manuscript/Mixed Material. Library of Congress (PWMASTER_114674). https://www.loc.gov/item/powmia/pwmaster_114674/. 

"Memorial Day and a Missing Brother." New York Daily News [New York, NY], June 1, 1989. 

Padilla, Victor. “Protestan Servicio Militar; Guerra Vietnam.” El Mundo [San Juan, PR], October 31, 1968. https://gpa.eastview.com/crl/elmundo/newspapers/mndo19681031-01.1.95.

Papleta Plebiscito. Model Ballot. 1967. José Celso Barbosa Statehood Library. https://www.scribd.com/doc/101231719/Papeleta-Plebiscito-1967. 

Puerto Rico. Mayaguez. 1940 U.S. Federal Census. Digital images. Ancestry Classroom.

Secondary Sources
“Acosta-Rosario, Humberto.” POW Network. Updated 2020. Accessed February 16, 2026. https://www.pownetwork.org/bios/a/a002.htm.

Black, Ashley Leane. “From San Juan to Saigon: Shifting Conceptions of Puerto Rican Identity during the Vietnam War.” The University of British Columbia, 2012. https://open.library.ubc.ca/media/stream/pdf/24/1.0072836/1.

Born, Kevin M, and Alexander F. Barnes. Desert Uniforms, Patches, and Insignia of the US Armed Forces. Schiffer Military History, 2016.

Cruz Mejias, Coraly. “Same War, Same Traumas: Vietnam Veterans Demand Better Treatment.” Global Press Journal [Washington, D.C.], October 24, 2022. https://globalpressjournal.com/americas/puerto-rico/war-traumas-vietnam-veterans-demand-better-treatment/.

“The First Battalion (Mechanized) Fifth Infantry Twenty-Fifth Infantry Division in the Viet Nam War 1966-1971.” 5th Infantry Regiment Association. Accessed February 16, 2026. https://classic.bobcat.ws/history1968.html.

Foley, Michael Stewart. “How the Vietnam War Prepared Puerto Ricans to Confront Crisis.” Waging Nonviolence. Updated October 6, 2017. Accessed February 16, 2026. https://wagingnonviolence.org/2017/10/puerto-rico-vietnam-war-hurricane-maria-independence/.

“Humberto Acosta-Rosario.” 5th Infantry Regiment Association. Accessed February 16, 2026. https://bobcat.ws/deceased-members/12423.

“Humberto Acosta-Rosario.” American Battle Monuments Commission. Accessed February 16, 2026. https://weremember.abmc.gov/s?q=*&type=16&criteria=title%3Dacosta-rosario&b=0&a=c&v=G.

“Humberto Acosta-Rosario.” Veterans Legacy Memorial, National Cemetery Administration. Accessed February 16, 2026. https://www.vlm.cem.va.gov/HumbertoAcostaRosario/48E50.

“Humberto Acosta-Rosario.” The Wall of Faces, Vietnam Veterans Memorial Fund. Accessed February 16, 2026. https://www.vvmf.org/Wall-of-Faces/167/HUMBERTO-ACOSTA-ROSARIO/.

“Humberto Acosta.” International Missing Persons Wiki. Accessed February 16, 2026. https://int-missing.fandom.com/wiki/Humberto_Acosta.

Kantrow-Vazquez, Michelle. “Bumble Bee Closing Mayagüez Plant after 50 Years, Leaving 260 Jobless.” News is My Business. Updated May 1, 2012. Accessed February 16, 2026.  http://newsismybusiness.com/bumble-bee-closing-mayaguez-plant-after-40-years-leaving-200-jobless/.

Martinez, Andrew, and Nichole M. Garcia. “#HuelgaUPR: The Kidnapping of the University of Puerto Rico, Students Activism, and the Era of Trump.” Frontiers in Education 3 (September 2018). https://doi.org/10.3389/feduc.2018.00084.

“Mayagüez, Puerto Rico (2025 Guide) – All You Need to Know.” PuertoRico.com. Updated May 15, 2023. Accessed February 16, 2026. https://www.puertorico.com/mayaguez.

Renza, Victor. “‘No. 1 Gun’: An M60 Machine Gunner in Vietnam Tells His Story.” HistoryNet. Updated October 6, 2021. Accessed February 16, 2026. https://www.historynet.com/no-1-gun-an-m60-machine-gunner-in-vietnam-tells-his-story/.

“Staff Sgt. Humberto Acosta-Rosario.” Defense POW/MIA Accounting Agency. Accessed February 16, 2026. https://dpaa-mil.sites.crmforce.mil/dpaaProfile?id=a0Jt0000000KYY3EAO.

“SSgt Humberto Acosta-Rosario.” Find a Grave. Updated June 2, 2012. Accessed February 16, 2026. https://www.findagrave.com/memorial/91238900/humberto-acosta-rosario.

“SSgt Humberto ‘Cuco’ Acosta-Rosario.” Find a Grave. Updated February 25, 2000. Accessed February 16, 2026. https://www.findagrave.com/memorial/255124/humberto-acosta_rosario. 

Staudenmaier, Michael. “Puerto Rican Independence Movement, 1898-Present.” In International Encyclopedia of Revolution and Protest. Immanuel Ness, Ed. Blackwell Publishing: 2009: 2766-2774. https://www.marxists.org/history/erol/ncm-8/history-independence-movement.pdf.

Staff Sergeant Acosta-Rosario was a machine gunner with B Company, 1st Battalion, 5th Infantry, 25 Infantry Division. On August 22, 1968, he was on reconnaissance near the Ben Cui rubber plantation, Tay Ninh Province, South Korea. When his unit came under fire he was listed as Missing in Action. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.
-Information provided by the American Battle Monuments Commission

A photograph of Humberto Acosta-Rosario taken in Vietnam on August 22, 1968, just a few days before he went missing. Individual Deceased Personnel File, National Archives and Records Administration.

A young man posing in Vietnam with his weapon.

Humberto Acosta-Rosario signed this document on October 4, 1967, acknowledging his service commitment of two years of active duty and four years of reserve duty. Portions have been redacted for privacy reasons. Official Military Personnel File, National Archives and Records Administration.

A typed document with Acosta-Rosario's signature.

Acosta-Rosario’s service photograph. 5th Infantry Regiment Association.

A young man in an Army dress uniform and hat.

Humberto Acosta-Rosario’s name is engraved on the Honolulu Memorial at the National Memorial Cemetery of the Pacific in Honolulu, Hawai‘i, 2026. Courtesy of the American Battle Monuments Commission.

Humberto Acosta-Rosario's name on the Honolulu Memorial.

Humberto Acosta-Rosario’s name is listed on El Monumento de la Recordación (the Memorial Monument) in San Juan, Puerto Rico.

A list of names on a black panel on a monument.

Humberto Acosta-Rosario’s father, Alfredo, applied to place a memorial marker to honor his son in Puerto Rico National Cemetery after he was officially declared dead, March 10, 1978. Portions are redacted for privacy reasons. National Archives and Records Administration.

Request by Alfredo Acosta to place a memorial marker for his son, Humberto.

A detailed report of the 1987 investigation to identify the whereabouts of Humberto Acosta-Rosario. Library of Congress (PWMASTER_114674).

A report of investigators trying to Humberto Acosta-Rosario's remains in 1987.

A summary of the investigations attempting to identify the whereabouts of Humberto Acosta-Rosario from 1975 to 1993. Library of Congress (PWMASTER_114674).

A summary of investigations attempting to identify the remains of Humberto Acosta-Rosario's remains.

A news release from the Department of Defense that Humberto Acosta-Rosario was declared Missing in Action as a result of hostile action, August 30, 1968. Together We Served.

A typed press release from the U.S. Department of Defense.

Humberto Acosta-Rosario (right) with an unknown friend, c.1968. Together We Served.

Two young men pose in front of an Army Airborne sign.

The Acosta-Rosario family lived in Puerto Rico before Humberto’s birth in 1940. His father, Alfredo, worked as a laborer in a factory. He lived with his wife, Carmen; his daughter, Carmen America; his mother-in-law, also named Carmen; and his sister-in-law, Gloria. Gloria worked out of her home as an embroiderer. National Archives and Records Administration.

The Acosta-Rosario family in the 1940 census.

Honolulu Memorial

Humberto Acosta-Rosario's Profile Picture

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