No major National Parks exist in New Jersey, however the state does have a national park unit, a soon-to-be unit and 3 National Trails. Both units are National Historical Parks.
National Park Units
The two units in Connecticut are the two National Historical Parks listed below. One of them is still in the process of being established, so you can certainly see many of the sites even with it not yet being an official unit.
This is an odd National Historical Park as its still in the process of becoming an official NPS unit. So I looked it up recently on the NPS app and National Park Site. Coltsville was designated as a national historic landmark in 2008 and in 2014 was authorized to become a National Historical Park. Sites include many factory and other locations related to Coltsville and Samuel Colt, the revolver and the industrial revolution in the United States. There’s no visitor center yet, but hopefully things will complete for it soon!
Weir Farm National Historical Park
Established in 1990, Weir Farm NHS commemorates the life and work of impressionist painter J. Alden Weir and other artists who lived/worked on the farm. These include Childe Hassam, Albert Pinkham Ryder, John Singer Sargent, and John Twachtman. The farm consists of more than 60 acres in Wilton, CT that served as a backdrop to many of artists work as well. Many of the buildings such as the barn, studio, and house still exist on the farm and plays roles in visitation of the site.
National Trails are trails that often span across states for various geological or historical nature. Three of these trails traverse Connecticut. They are also national park service administered (with cancellation stamps) but are so diverse and connect across various parks and other sites that its not necessarily just one spot to visit.
Appalachian National Scenic Trail
One of the most famous trails in the US and possibly the world, the AT as it is affectionately called spans nearly 2,200 miles from Maine to Georgia along the Appalachian Mountain Range. Conceived in 1921 and completed in 1937 the trail is managed by the NPS and maintained by over 30 trail clubs along it’s span.
Hundreds of thru-hikers and thousands more shorter hikes touch the trail each year. About 48 miles of the Appalachian Trail pass through Connecticut.
New England National Scenic Trail
The New England NST is a trail that traverses nearly 235 miles from Connecticut through Massachusetts and to the border with New Hampshire. The trail travels north/south through the states. The trail connects three trails, the Mattabesett Trail, Metacomet Trail, and Metacomet-Monadnock Trail. The highest point of the trail is Mount Grace (1617ft) and the lowest Long Island Sound (sea level). [ CT MA ]
Washington-Rochambeau Revolutionary Route National Historic Trail
In the Year 1781, French General Rochambeau joined Washington’s Army in Yorktown VA in an effort to fight the British Army. With Support of French Naval Vessels, the Army moved Troops hundreds of miles in what would be the largest troop movement of the American Revolutionary War. This trail protects parts of the original trail that Americans used to travel to Yorktown from as far away as New Hampshire. The historic trail has sites to visit from Massachusetts to Virginia.
In Connecticut travelers can visit Lebanon Green, which was used by the French Cavalry for Winters Quarters between 1780 and 1781. [ MA RI CT NY NJ PA DE MD VA DC ]
Check out Nearby States National Park Sites
New York | Rhode Island | Massachusetts