Baseline Road is a major east-west street in Boulder, Colorado that extends east of the city through parts of four counties. The western terminus of Baseline Road is at Flagstaff Mountain in the . The eastern terminus is at 16800 Watkins Road, about 6 miles (9.7 km) east of Lochbuie on the boundary between Adams and Weld Counties. The total length of Baseline Road is approximately 38 miles (61 km), all of which is within the Denver-Aurora-Boulder Combined Statistical Area in Colorado. Baseline Road runs almost exactly along the 40th line of latitude.