Montana became a part of the United States in the Louisiana Purchase, and Lewis and Clark got there in 1805 to check the joint out. Fort Benton was the first settlement in 1859. Gold and silver brought folks out in the 1860s, and it was included in the Idaho Territory in the early 1860s, and it became a Territory of its own in 1864. Montana became a State in 1889, the 41st.