From their website:

The Historic Jersey City & Harsimus Cemetery is a National Treasure. Prior to the creation of the Cemetery in 1829, it’s historical significance dates back to the 1700’s as the site of Revolutionary War skirmishes, and an active Ammunition Bunker during the War of 1812 that still stands proudly on our grounds. Now the sacred eternal resting place of thousands of soldiers from the Revolutionary & Civil Wars, the War of 1812, the Spanish-American War, WWI and II, forward, as well as home to our earliest Jersey City founders, leaders, residents and legends. With its 200 year old English Ivy adorning many of the towering trees, and the monumental works of art, this 6-acre sanctuary of peace and unique history is one of the most beautiful natural settings in Jersey City.

Learn more by visiting their website, which includes a timeline of the history of this park which goes back to the mid 1700s.