The Delaware Water Gap formed 500 million years ago[4] when quartz pebbles from mountains in the area were deposited in a shallow sea.

The Martinsburg Shale on the eastern side of what was to be Kittatinny Mountain was uplifted 450 million years ago when a chain of volcanic islands collided with proto-North America.

During this period, the Delaware River slowly cut its path down through the shattered and cracked quartzite.

[5] Millions of years of rain, ice, snow, and wind erosion shaped the area.

The Silurian High Fall formation of sandstone is on the western side of the gap near the base.

In 1739, America's first botanist, John Bartram of Philadelphia, followed the course of the Delaware River in his search for American trees, evergreens and shrubs to supply new species that were formerly unknown to British naturalists.

Using Native American trails, Bartram rode on horseback through the Water Gap, which allowed entry to the lands beyond.

Hardwood species comprising the forest include various oaks, hickories, maples, ash, elm, cherry, walnut, birch, sycamore, and beech.

Steep rock walls prohibited foot travel through the gap until a road was built on the Pennsylvania side of the river in 1793.

The Pennsylvania Northeast Regional Railroad Authority owns the trackage in the Water Gap area.

Martz Trailways has a bus station within the municipal boundaries of Delaware Water Gap.

There are also numerous jitneys that stop there on their route between New York City and towns further areas such as Hazleton, Wilkes-Barre, and Scranton.

In 1962, the Congress authorized the building of a dam across the Delaware River at Tocks Island, upstream of the water gap.

The land for the proposed reservoir, which had already been purchased, was used to create the Delaware Water Gap National Recreation Area in 1965.

The most challenging hike in the park is to combine the Red Dot and Blue Blaze trails into a 3 mi (4.8 km) loop.

The trail crosses Route 206 and continues along the ridgeline of the Kittatinny Mountains to High Point State Park, eventually entering New York.

Beginning in 2010, the Pennsylvania side has been periodically closed to climbing during the nesting season for the endangered peregrine falcons.

Camp Minsi is now located in Pocono Summit, Pennsylvania, on the shores of Stillwater Lake.