He was born in Slaidburn, West Riding of Yorkshire, England in 1825, and moved to the United States at the age of 23, arriving in New York City but moving on to Buffalo, New York, where he went into the slaughtering business for a couple of years. In 1850, he sold out and moved to Wisconsin, and became a farmer and rancher. In 1851, his younger brother Thomas Sanderson left Slaidburn and came to Wisconsin with his wife and children, joining his brother in Columbia County. In 1856, Robert Sanderson married Mary Currie, daughter of an immigrant from Scotland. From 1858–1860, he was on the town board of Springvale in Columbia County, serving in 1860 as its chairman. His brother Thomas was treasurer of Springvale in 1859. As of 1862, when he first appeared in the Assembly, he was 36 years of age, and had been in Wisconsin for 12 years; he was at that time a resident of Cambria, and a member of the Republican Party.
Legislative service
He was first elected to the Assembly for the 1862 session, representing the 3rd Columbia County district. He was assigned to the standing committee on railroads. He was succeeded in the 1863 term by Yates Ashley, a fellow Republican.
Sanderson returned to the Assembly for the 1866 session, but this time from the 2nd Columbia County district, succeeding Jesse Hand, another farmer and member of the Union Party. He was assigned to the committees on the expiration and re-enactment of laws; and on agriculture and manufactures. In 1867, Sanderson advanced to the Senate to represent the 25th Senate District ; and was assigned to the committees on roads, bridges and ferries; and on engrossed bills. He was also a member of the Board of Regents for the University of Wisconsin. He returned in 1868, although by that time the Union Party label had been abandoned; he was assigned to the committees on privileges and elections; on agriculture; and on railroads. He was re-appointed to a new term as a regent, and would serve in that capacity through 1873, including serving on the executive committee of the Board of Regents. He was succeeded in 1869 by fellow Republican William M. Griswold.
After the legislature
By 1870, he had moved to "'76 Farm" in Dane County four miles outside of Madison, where he raised Clydesdales, shorthorn cattle and other livestock. In 1870, he was the unsuccessful candidate for the 2nd Assembly district of that County against DemocratKnudt Heimdal, with 751 votes to Heidal's 858; but his brother Thomas was elected to Robert's old 2nd Columbia County Assembly seat at that same election. In 1871, Robert was one of the directors of the Chicago and Superior Railroad Company. He was also involved in the creation of the Madison and Portage Railway.
In 1876 Sanderson sold all his interests in Wisconsin and moved to Texas, whose climate and custom of free range husbandry suited his preferences. After a period as a sheep dealer in San Antonio, he joined his sons in a partnership with J. I. Case and Eli Stilson, raising cattle and sheep. When the partnership dissolved, Case and Stilson took the cattle, and the Sandersons moved to San Angelo, where they continued mostly in the sheep business. When the San Angelo National Bank was organized, Sanderson was elected its president, and held that office until his death on June 18, 1887. He and Mary Currie Sanderson had four sons and two daughters.
