Veterans Memorial Park, Avon Lake, OH

This is may be as far west as you'll see good stones on Lake Erie - a small oasis of Ohio Shale.  The beach is small, and it's a popular site - so expect the selection may be a little limited.  But, yea, there be rocks.  The black stones are astonishingly frail - they're weathered to the shape of a good skipper, and will crumble in your hand with little pressure.

Riverfront Park, Franklin PA

Home of the Rock in a River Festival, a mecca of North American Stone Skipping.

Riverfront Park is situated at the confluence of French Creek and the Allegheny River - creating a broad, shallow Shangri-La for skipping.  You won't find a lot of rocks on the beach, but a walk into knee-deep water will likely turn up stones from the previous festival.  

Riverfront Park was home court to skipping legend Russ "Rock Bottom" Byars (1962-2017)

Pebble Beach, Door County, WI

Just off Hwy 42 in Sister Bay, Wisconsin is a quiet beach with some choice skippers.  This is a personal favorite rock skipping beach, and has a great combination of stones and calm water.  The beach is protected by a small bay in Wisconsin's Door County peninsula; on a calm day, there are practically no waves.

Parking is limited to the access road, and there are private homes along the beach.

The stones are Dolomit from the Silurian Period - nearly 450 million years old.  It's a harder, less platy rock than shale and limestone - and presumably a little tougher to find a very flat skipper.

image courtesy of lundquistrealty.com