Missoula County became a part of Montana Territory when the territory was organized out of the existing Idaho Territory by Act of Congress and signed into law by President Abraham Lincoln on May 26, 1864. At this time Deer Lodge County (today Deer Lodge, Granite, Silver Bow, and Powell Counties) was cut out of Missoula. The creation of Flathead (today Flathead and Lincoln Counties) and Ravalli Counties in 1893, Powell in 1901, Sanders in 1905, Mineral in 1914 and finally Lake County in 1923 gave Missoula its present borders.