He settled in that part of
Idaho Territory, which later became Montana, where he engaged in the practice of law and also became interested in mining and stock raising. He was a young lawyer when he moved to Montana (
Bannack) in 1863. He was there before courts were organized and, being one of the first permanent settlers, took a prominent part extralegal activities in the territory. He was a founder of the infamous
Montana Vigilantes, using his position as a lawyer to cover for the gang's summary murders. In December 1863, Sanders led the prosecution of
George Ives as the murderer of Nicolas Tiebolt in
Nevada City, Montana. Ives was convicted and hanged on December 21, 1863. The George Ives trial initiated a period of
vigilantism, extrajudicial killings orchestrated in part by Sanders that eventually brought an end to thefts and murders by "
road agents" in the Virginia City region. Sanders was one of the five original organizers of the Alder Gulch Vigilance Committee, which was formed on December 23, 1863 in Virginia City, Montana. As a ringleader of the Vigilantes, Sanders was implicated in the mysterious 1867 death of acting territorial governor
Thomas Francis Meagher, who had opposed vigilantism and its associated Freemasonry and Protestantism. Meagher was also a formidable political opponent well-positioned to outrun Sanders in any future bid for office once Montana was granted statehood. In his career as an attorney, Sanders gained a reputation for representing minority defendants, including Chinese and Indians. In a sensational 1881 trial, Sanders led the defense for Ah Wah and Ah Yen, Chinese miners on trial for murder. Sanders argued reasonable doubt and lack of evidence, and the
Montana Territorial Supreme Court acquitted the defendants. In 1873, Sanders became a member of the Territorial Legislature. Also, he realized the importance of preserving early records and was for thirty years the president of the
Montana Historical Society, established in 1865. He accumulated newspapers and documents in his law office. Sanders was a founding member of the
Society of Montana Pioneers and served as its secretary (1884) and president (1888). He unsuccessfully ran as a
Republican candidate for the US House of Representatives in 1864, 1867, 1880, and 1886 and was a member of the Territorial House of Representatives of Montana from 1873 to 1879. He was the first president of the board of trustees of
Montana Wesleyan University, which opened in 1890 in
Helena. ==State of Montana==