A deep, narrow gorge cut through the Kittatinny Mountains east of Stroudsburg, Pennsylvania. The Delaware River carved the winding path out of solid rock millions of years ago. The gap is about 3 miles long and has steep walls that rise more than 1,200 feet on each side. Highways follow the river's path through the gorge. Mount Tammany stands on the New Jersey side of the gap, and Mount Minsi is on the Pennsylvania side. The gap and the area around it form the Delaware Water Gap National Recreation Area.