Asa Maupin was born around 1826 in Albemarle County, Virginia. He was a slave of Virginian Lilburn G. Maupin, who moved from Albemarle to Monroe County, Missouri, sometime in the 1840s. Maupin married Eliza Arnold Maupin in slavery on September 10, 1853, at the home of Eliza's master, Harvey Arnold, in Monroe County. Together they had eight children: Dorian, born November 20, 1854; Thomas, born September 14, 1857; Eliza Jane, born December 25, 1860; and five children whose names are not known. Maupin gave his occupation as farmer when he enlisted.

Maupin enlisted as a private at the age of 38 on October 2, 1864, in Mexico, Missouri, and mustered in on October 11 at Benton Barracks in St. Louis. His service record describes him as 5 feet, 3 inches tall, with black hair, black eyes, and a black complexion. He served in Company C of the 18th USCT Infantry Regiment. The regiment was eventually transferred east, where on November 24, Maupin served on detached duty in Paducah, Kentucky. He became sick in the winter and died at the general hospital in Nashville, Tennessee, on January 25, 1865. Records suggest he died of diarrhea, although his wife and a comrade suggested he died of smallpox contracted while tending to his sick comrades.

Following Maupin's death, his wife continued to live in Paris in Monroe County. In 1866, she began receiving a pension of $8 a month, plus $2 for each of her minor children. She later applied for an increase, but it is unclear if she ever received one.