Trump won Montana 56.92% to 40.55%, a margin of 16.4%, down from the 20.4% margin he scored four years earlier. Prior to this election, most news organizations considered this a state Trump was very likely to win, or otherwise considered a likely red state. Montana has not been won by a Democrat since 1992, and has only been competitive in two elections since then, namely in 1996 and in 2008.
Despite his loss in the state, Biden was able to flip Blaine County, a bellwether that is home to Fort Belknap Indian Reservation. He also narrowed Trump's margins in 31 other counties, including the counties of Lewis and Clark (Helena, the state capital), and to a lesser extent Roosevelt, which holds most of Fort Peck Reservation. Additionally, Biden even widened Hillary Clinton's margin of victory in every other county that she won in 2016. This is the first time since their creation in 1919 and 1912, respectively, that a Democrat has won a presidential election without carrying Roosevelt or Hill county.