Clark
- County:
- Mercer County
- County Seat:
- No
- Area (mi²):
- 3.011
- State:
- Pennsylvania
Clark is a borough located in Mercer County, Pennsylvania. Clark has a 2026 population of 559. Clark is currently declining at a rate of -0.53% annually and its population has decreased by -2.78% since the most recent census, which recorded a population of 575 in 2020.