Thomas Jefferson Harlin/Harlan Born TN Civil War Vet?

I’m looking for the Civil War regiment that Thomas Jefferson Harlin/Harlan served in during the Civil War. The 1870 Census shows him living in Yolo County, California, born Tennessee, age 32, so born 1838.The 1910 Census shows him living in Orange, Orange County, CA.Thomas died December 10, 1923 age 85 years and is buried in an unmarked grave at Santa Ana Cemetery in Santa Ana, Orange County, California.Lafayette Harlin/Harling (1836-1889) a Civil War Veteran of the 9th KY is buried two graves away.Maybe they are brothers?Our Sons of Union Veterans of the Civil War (SUVCW) Camp needs to find the unit he served in so we can order him a Civil War Monument for a grave dedication planned for Memorial Day 2009.