St. Johnsbury is a census-designated place (CDP) corresponding to the main settled areas in the town of St. Johnsbury, Caledonia County, Vermont, United States. As of the 2020 census it had a population of 5,994, out of 7,364 in the entire town. The CDP is in eastern Caledonia County, occupying the southern one-third of the town of St. Johnsbury. It includes the urban center of St. Johnsbury, the village of St. Johnsbury Center to the north up the valley of the Passumpsic River, and development along Route 2 to the east up the valley of the Moose River, but not as far as the village of East St. Johnsbury. Interstate 91 passes through the west side of the CDP, with access from Exits 20, 21, and 22. I-91 leads north 42 mi to Newport and south 59 mi to White River. U.S. Routes 2 and 5 intersect in the center of the community. U.S. 2 leads west 35 mi to Montpelier, the state capital, and east 28 mi to Lancaster, New Hampshire, while U.S. 5 provides a local parallel route to I-91, leading north 8 mi to Lyndonville and south 20 mi to Wells River.