Columbia is a planned community in Howard County, Maryland, United States, consisting of 10 self-contained villages. With a population of 104,681 at the 2020 census, it is the second-most-populous community in Maryland, after Baltimore. Columbia, located between Baltimore and Washington, D.C., is part of the Baltimore metropolitan area and is tracked by the United States Census Bureau as a census-designated place. Columbia proper consists only of territory governed by the Columbia Association, a not-for-profit management company. The United States Postal Service also uses the name for other communities that predate Columbia, including Simpsonville and Atholton; the Census Bureau also counts part of Clarksville as Columbia. Developer James Rouse founded Columbia in 1967, aiming to create a community that would avoid the inconveniences of then-current subdivision design; eliminate racial, religious and class segregation; and reduce leapfrog and spot zoning development.