Thorndale is a census-designated place in Caln Township, Chester County, Pennsylvania, United States. The population was 3,407 at the 2010 census. Thorndale is the commercial and administrative center of Caln Township. The community's main street is U.S. Route 30 Business. Many of Thorndale's old houses fell into disrepair from the late 1990s to present and have been torn down and replaced with new businesses. Thorndale is historically notable for containing a summer house of U.S. President James Buchanan, which still stands and has been incorporated into a golf course and turned into a restaurant.