Interstate 540 (I-540) is a freeway spur route of I-40 in the US state of Arkansas in Fort Smith. The total length is . At first, I-540 was a short spur connecting Fort Smith and Van Buren to I-40 as one of the original five Arkansas Interstates. The route ran just over to US 271 near the Oklahoma state line. The growing Northwest Arkansas area and the University of Arkansas needed an Interstate connection to Little Rock, and through traffic north to Kansas City had also outgrown the winding US 71 north from I-40. The route was extended north to Mountainburg in the late 1990s on an all-new alignment, (Going under concurrency with I-40, one of the only auxiliary routes with a concurrency with its parent) with the route being completed to Bella Vista in January 1999. However, the segment north of I-40 became a part of Interstate 49 in 2014.