Robert Williams, Jr., was born on January 24, 1841, in Chambersburg, Pennsylvania, to Robert and Elizabeth Williams. His father was a cooper who owned $1,000 of real estate and $600 of personal property by 1860. The family moved to Camden, Ohio, in the 1850s, and Williams attended school there.
Williams enlisted in the Union army on April 18, 1861, and he mustered in as a private in Company B of the 20th Ohio Infantry on April 27. He was promoted to sergeant on May 27, and he mustered out on August 18, 1861. He returned to the Union army soon afterward, receiving a commission as captain in Company B of the 54th Ohio Infantry on September 11, 1861. The regiment took part in the Battle of Shiloh, the siege of Corinth, the Vicksburg campaign, the Battle of Missionary Ridge, and the Atlanta campaign. He was severely wounded in the Battle of Chickasaw Bayou in December 1862, but he eventually recovered and rejoined the regiment. He was promoted to major in the fall of 1862, and then to lieutenant colonel on September 29, 1863. He mustered out on September 14, 1864.
Williams married Elvira Elliott on July 8, 1863, and they had at least five children: Sherman, born around 1865; Carrie, born around 1867; Nellie, born around 1868; Eva, born around 1871; and Bessie, born around 1876. He settled in Dayton, Ohio, after the war and earned a living as a revenue collector. By 1870, he owned $2,000 of real estate and $3,500 of personal property, and he employed at least one white domestic servant.
They moved to Eaton, Ohio, in the 1870s. He supported the Republican Party, and he served several terms in the Ohio legislature. He was also a skilled archer who won national championships in 1883, 1885, and 1902. During the 1904 Summer Olympics in St. Louis, Missouri, he won two silver medals in archery, and he won a gold medal in the team competition. By the early 1900s, he was living in Washington, D.C. He died of pneumonia on December 10, 1914.