Hatfield Swamp is a fresh water wetland area in the U.S. state of New Jersey, forming what might be considered the "second bank" of the Passaic River between Morris and Essex counties.
Over millions of years, the rift valley was faulted, tilted, and eroded, until the edges of the hard flood basalt layers formed ridges.
As the glacier eventually melted back, water pooled behind the ridges (known today as the Watchung Mountains), forming Glacial Lake Passaic.
During the struggle, the properties of Hetfield, an acknowledged Loyalist, were confiscated and sold to Cyrus Crane, who operated a mill on the edge of the swamp in what is now West Caldwell.
After the death of family member Herbert Crane in the 1960s, the mill was dismantled and moved to Allaire State Park in Monmouth County, New Jersey.
The Hatfield Swamp floods several times a year, from heavy rain, snow melt in spring, or the remnants of storms that originated in the tropics.