Robert Short was born on March 31, 1823, to James and Eleanor (née McFarland) Short in Fairview, Pennsylvania. After apprenticing as a tailor he worked in Delaware and Gallion, Ohio before entering Ohio Wesleyan University in 1841. He left college the next year and was a school teacher from 1843 to 1844, before returning to tailoring in 1845 in Illinois. Short then worked as a farmhand in 1846 before heading west to the then Oregon Country in 1847 with Joel Palmer and Joseph C. Geer. Settling in Oregon City, he opened a tailoring shop before heading south to the gold mines of California from 1849 to 1850. He married Mary Geer on February 19, 1848, and they had six children.