Washburn was born in Livermore, Maine. A graduate of Bowdoin College, he moved to Minneapolis, Minnesota around 1857 to practice law and work for the Minneapolis Milling Company (founded by his brother Cadwallader). His business ventures in lumber and flour milling allowed him to amass a large fortune, and by the 1880s, he was among the wealthiest men in Minnesota. Washburn served as the first president from 1883 to 1889 of what was to become Soo Line Railroad.[1] He built a mansion known as "Fair Oaks" in 1883. It was designed by E. Townsend Mix, who also designed Minneapolis's Metropolitan Building, and the outdoor landscape was laid out by Frederick Law Olmsted. The grounds included an artificial stream leading to a pond, a rustic footbridge, a greenhouse, and a carriage house. The home was demolished in 1924 to make way for a park, although the region is now part of the Washburn-Fair Oaks Mansion District, which was added to the National Register of Historic Places in 1977.
He was elected to the House of Representatives in 1878 and served from March 4, 1879 to March 3, 1885. He was elected to the Senate in 1888 and served from March 4, 1889 to March 3, 1895.
Washburn was a founder of the First Universalist Church of Minneapolis in 1859. A major benefactor, he served as a trustee and President for much of his remaining life. He died in Minneapolis.