The Mineral Springs Loop Trail at Raccoon Creek State Park in Hookstown, Pennsylvania is an easy 1.4 mile loop hike to a mineral spring and a seasonal waterfall - a large cave-like overhang also known as Frankfort Mineral Springs Falls. Parking can be found at the park's office right on route 18 in the middle of the park and the trailhead is on the southern part of the parking lot.
Depending on the time of the year, the mineral spring comes down as a waterfall along the overhang and feeds into the adjacent creek. Small fish can be found along the creek as well. Fishing is permitted with a state license.
Waterfall: The main waterfall can be found on the left side of the cave and the mineral springs is mostly found on the right side of the cave overhang; however, when I was visiting, the main falls on the left was dried up. The main falls on the left side is about 8 feet tall and usually runs if there's been heavy rain or during the wetter seasons. The mineral springs fall (smaller) tends to run year-round.
History: Frankfort Mineral Springs Falls used to be the main attraction at the Frankfort Hotel and Resort, which was built in the mid-1800's. Visitors would drink from the springs and believed that the water would help cure ailments like indigestion and kidney disorders. The hotel closed after a fire in the 1920's. It's not recommended that you drink from this spring without a water filter since the water is often tinted a strange orange due to its high iron content that you can see is left on the cave's rocks in the pictures.
For other interesting waterfall hikes near Pittsburgh, be sure to check out Fall Run Falls Trail in Glenshaw, Pennsylvania - just north of the city.