Silas Sanford Smith, Jr. (October 26, 1830 – October 11, 1910) was a Mormon pioneer, a politician in the Utah Territory, and the leader of the San Juan Expedition that settled San Juan County, Utah.Smith was born in Stockholm, New York. His father, Silas Sr., was a younger brother of Joseph Smith, Sr., which made Silas Jr. and Joseph Smith, Jr. first cousins. Silas Sr. was baptized into Smith's Church of the Latter Day Saints in 1835 and the family became followers of Smith.