Addison is a borough in Somerset County, Pennsylvania, United States.

[4] A schoolhouse was constructed about 1832, and a foundry was begun by Thomas & Nathan Cooper in 1844.

According to the United States Census Bureau, the borough has a total area of 0.6 square miles (1.6 km2), all land.

The Petersburg Tollhouse, one of several toll houses on that road, is now listed on the National Register of Historic Places.

About 5.1% of families and 13.9% of the population were below the poverty line, including 6.1% of those under the age of eighteen and 25.4% of those sixty five or over.