Riley Carpenter was born on August 12, 1821, in Brattleboro, Vermont, to Abner and Nancy Carpenter. He eventually moved to Richmond, Pennsylvania, and married Lovicy Pratt. They had at least eight children: James, born around 1849; Emma, born around 1851; Eva, born around 1853; Lydia, born around 1855; Martin, born around 1858; Lilly, born around 1859; Riley, born around 1862; and Harriet, born around 1868. He worked as a farmer, and by 1860, he owned $3,000 of real estate and $600 of personal property.
He enlisted in the Union army on August 30, 1862, and mustered in as a private in Company C of the 150th Pennsylvania Infantry later that day. The regiment took part in the Battle of Chancellorsville, the Battle of Gettysburg, the Overland Campaign, the siege of Petersburg, and the Appomattox campaign. He mustered out on June 23, 1865.
Carpenter returned to Richmond after the war and resumed his work as a farmer. By 1870, he owned $6,000 of real estate and $1,820 of personal property. He applied for a federal pension in July 1890, suffering from rheumatism and chronic diarrhea. He remained in Richmond for the rest of his life, and he died there on July 21, 1910, after fracturing his femur in a fall.