Maria Mercedes "Mercy" Garcia Aguilera was born in 1936 to Manuela Garcia Sanchez and Joseph Mendez Garcia in the Cook's Point area of Davenport, Iowa. Joseph Mendez Garcia, born in Mexico, and Manuela Garcia, from Texas, met while employed as migrant laborers. The couple moved to Cook's Point in the 1930s when Garcia's father found work as a section hand with the Rock Island Railroad. They had fifteen children.
Maria Garcia's childhood in the predominantly Mexican and Mexican American community of Cook's Point was marked by poverty. The family lived in a house with no plumbing and at age five Garcia began helping her mother perform household duties such as collecting coal from the nearby railroad tracks and carrying water from the local pump. At eight years old she obtained seasonal work topping onions with her older sister and other members of the Cook's Point community.
Maria Garcia attended St. Alphonsus School in Davenport. After completing the seventh grade she moved with her sister to live with a family in Toledo, Iowa, and attended St. Joseph's School for one year. Garcia then moved to Ottumwa, Iowa, to live with the Roberts family where she assisted with household duties. She stayed there for four years, and attended school for one year during that time. In 1956 she returned to her family in Buffalo, Iowa, following the death of her younger brother Bobbie in a drowning accident.
At age seventeen Garcia obtained her first factory job as a cable lacer in Chicago, Illinois, where she lived with her sister, Ramona. Her next job involved soldering juke boxes for Rockacola Company. In 1957 Garcia's first child, Lisa, was born. She married Peter Aguilera, a factory worker, in 1960 and a year later their son, Peter Jr., was born. The couple moved to Iowa City, Iowa, in 1963 when Peter Aguilera secured a job with International Harvester Company (IHC) Farmall. They later purchased a home and settled in Davenport.
In 1973 Maria Aguilera applied for a job at IHC Farmall and was denied work on the grounds that she was too short. Aguilera, suspecting discrimination, pressured the company and was hired to work on the assembly line. Maria Aguilera worked for International Harvester Company Farmall until 1982 when the plant closed down. Following this she worked for a variety of Davenport businesses including Brach's Candy Company, Good Samaritan Nursing Home, and Bishop's Cafeteria. In 1992 the Aguileras adopted a daughter, Kayla, and one year later Maria Aguilera retired from paid employment although she continued to work as a volunteer in the local schools for several years.