Lewis Allen Grimes was born on November 6, 1839, in Adams County, Ohio, to Greer and Sophia Grimes. His father was a farmer who owned $6,400 of real estate by 1850. He grew up and attended school in Monroe, Ohio.
In April 1864, he received a commission as an assistant surgeon in the 32nd Ohio Infantry. The regiment took part in the siege of Atlanta. He resigned on July 23, 1864.
Grimes settled in Concord, Kentucky, after leaving the army. He married a woman named Amanda, and they had at least two children: Claude, born around 1870; and Mary, born around 1872. He worked as a physician, and by 1870, he owned $500 of personal property. His wife died in September 1879.
He married a woman named Mary around 1884, and their son Archibald was born in September 1884. He applied for a federal pension in June 1892 and eventually received one. He remained in Concord for the rest of his life, and he died there of arteriosclerosis on June 20, 1921.