Samuel Walker was born in Franklin County, Pennsylvania in 1822. After marrying Marian E. Lowe, Walker moved to Ohio in 1848, and in 1855, he settled in Lawrence, Kansas. Later that year, Walker became a member of the Bloomington Guard and was elected first sergeant. In the following year, Walker was elected colonel of the 4th Kansas Cavalry and participated in campaigns during Bleeding Kansas, including commanding a force of free-staters during the Battle of Fort Titus outside of Lecompton, Kansas on August 16, 1856. The battle was in retaliation for the 1856 sacking of Lawrence. Walker would later become a Deputy U. S. Marshal and sheriff of Douglas County, Kansas, from 1857 to 1862.

In 1861, Walker was commissioned as the captain of Company F, 1st Kansas Volunteer Infantry Regiment and commanded the company at the Battle of Wilson's Creek, Missouri. Walker was then promoted to major of the 5th Kansas Volunteer Cavalry Regiment in 1862 before being promoted to lieutenant colonel of the 16th Kansas Volunteer Cavalry Regiment in 1864.

At the end of the Civil War, Walker again served as the sheriff of Douglas County from 1868 to 1872 before being elected City Marshall in 1872. Walker also served in the Kansas State Senate from 1872 to 1874. Walker passed away in Lawrence in 1893.