Erastus C. Smith (1810January 26, 1891) was an American businessman, politician, and pioneer of Rock County, Wisconsin. He served one term in the Wisconsin State Assembly, representing the southwest quadrant of Rock County during the 3rd Wisconsin Legislature (1850). He was elected to the Assembly on the Free Soil Party ticket, and became a Republican when that party was established in 1854. He was one of the earliest American settlers in what is now the town of Spring Valley, Wisconsin. His name was often abbreviated as E. C. Smith.

Biography Erastus C. Smith was born in 1810 in New York state. He resided in Clinton County, New York, and Oneida County, New York, before moving west to the new state of Wisconsin. He was one of the earliest settlers in the newly-established township of Spring Valley, Rock County, Wisconsin, arriving in 1846.

He served three years as postmaster at Spring Valley, and was elected to the Wisconsin State Assembly in 1849, running on the Free Soil Party ticket. He served the district that included the towns of Avon, Center, Newark, Rock, and Spring Valley in Rock County, Wisconsin.Wisconsin Legislative Reference Bureau. "Members of the Wisconsin Legislature 1848–1999" Information Bulletin 99-1, September 1999. p. 108. In the 3rd Wisconsin Legislature, he was assigned to the standing committees on privileges and elections; and on expiration and enactment of laws.Journal of the Assembly of the Third Legislature of the State of Wisconsin Madison: David T. Dickson-State Printer, 1850; pp. 5, 11

In 1854, the Republican Party was created from a fusion of Whigs and Free Soil Democrats, and Smith became a member of the new Republican Party. He was elected treasurer of Rock County in 1856, running on the Republican ticket, and served a two year term.

In the late 1850s, Smith moved into the city of Janesville, Wisconsin. In 1860, he was appointed a city assessor in Janesville. In 1866 he purchased a grocery store and operated it for several years, and built a large storehouse in the city. In 1882, he became a shareholder in a boot factory in Janesville.

Smith died at his home in Janesville on January 26, 1891, after suffering from stroke paralysis for two years. His body was interred at Janesville's Oak Hill Cemetery.

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