Monroy was born in Douglas, Arizona on 11 May 1912. He moved to Napa Valley, California in the early 1930s, settling in St. Helena in 1933, and learnt Italian and Spanish whilst working at Beringer Brothers, a winery still operating during the prohibition.

By the breakout of World War II, Monroy was working as a shipfitter at Mare Island. He enlisted in 1942, aged 30, and was assigned as a mechanic for the Army Air Corps in Guam and the Mariana Islands. He survived being shot down in a B-25 aircraft over a small South Pacific island, and was then interrogated, giving up “nothing but name, rank, and serial number” until the U.S. marines retook the island.

In 1941, before he enlisted, Monroy married Mexican-born Maria Boucsieguez Cardoza, and the couple had seven children. He built his own house in 1949 and remained there until his death. He and his wife were married for 70 years.

After the war’s end, Monroy was employed as a flight engineer at what is now Travis Air Force Base. He was away from home for a week during the 1962 Cuban missile crisis. He was also a vocational arts aide and teacher of English as a Second Language (ESL) at St. Helena High School.

Upon turning 110, Monroy became the third Arizona-born person to reach supercentenarian status, after Carmen Amado Acevedo in 2019 and Irene Eskey in 2020. He died on 7 January 2023 at the age of 110 years, 241 days, being among the top five oldest men in the United States, and was survived by six of his seven children, as well as 10 grandchildren and five great-grandchildren.