[4] It is located 2 mi (3.2 km) north of Pottsville in the southern Coal Region.

St. Clair is noted for manufacturing squibs, fuses and caps used in the mining industry.

Mill Creek, which runs through the center of St. Clair, is the site of the annual Brindled Dhow Floating Expo.

The event, held the first weekend each October, draws model dhow enthusiasts from across the region[citation needed].

According to the United States Census Bureau, the borough has a total area of 1.2 square miles (3.1 km2), all land.