Robert B. Crandall was born around 1839 in Mississippi to David and Priscilla Crandall. His father was a farmer who owned $6,000 of real estate and $450 of personal property by 1860. The family moved to Adams, Wisconsin, around 1846 and then to Baraboo, Wisconsin, in the 1850s. By 1860, Crandall was working as a farmer.
He enlisted in the Union army on August 14, 1862, and he mustered in as a sergeant in Company F of the 23rd Wisconsin Infantry. The regiment took part in the Vicksburg campaign and the Red River campaign. In December 1862, he assured his family that he had “the courage to face dangers,” and he was “confident I shall live to see you all again.” In December 1863, he noted that he “had to make out election returns for the Co[mpany],” and he cheered that the “votes were straight Union.” He was promoted to 2nd lieutenant on March 31, 1863, and he mustered out on July 4, 1865.
He returned to Wisconsin after the war, and he married a woman named Alice around 1865. They had at least three children: Morris, born around 1867; David, born around 1868; and Jessie, born around 1876. Crandall supported the Republican Party, and local Republicans nominated him for county superintendent in 1867. They moved to Nassau County, Florida, around 1869, and Crandall worked as a farmer there. By 1870, he owned $300 of real estate. They moved to the Dakota Territory in the 1870s and then to Olympia, Washington, in the late 1800s. He worked as a bailiff for the state supreme court. He died of tuberculosis in Olympia on October 10, 1901.