At 24-years of age, he went to Pueblo and established a law practice there.[1]
In 1869, President U.S. Grant appointed Thatcher to serve as United States Attorney for Colorado Territory. Thatcher resigned the position after serving a little more than a year and returned to private practice.[1]
In 1876 he was elected as a Republican to the Colorado Supreme Court and immediately became the state's first chief justice. He got the position by luck. To create staggered terms for the state's first Supreme Court, one of the newly elected justices was to have a term of three years, the others having longer terms. However, the law stipulated that the person who drew the lot for the shorter term would become Chief Justice, and Thatcher drew the shorter straw.[1]
Death
Thatcher died of kidney failure in San Francisco on March 20, 1884, at 41. He is buried at Roselawn Cemetery in Pueblo.[2]