County Route 521 (CR 521) is a county highway in the U.S. state of New Jersey. The highway extends 43.71 miles (70.34 kilometers) from High Street (CR 519) in Hope Township to the New York state line in Montague Township. CR 521 follows portions of the Military Road, a roadway built during the French and Indian War connecting Elizabethtown, New Jersey (now Elizabeth) with a string of fortifications constructed along the Delaware River in modern Sussex and Warren Counties in northwestern New Jersey. Route description CR 521 begins at an intersection with CR 519 and CR 609 in the community of Hope in Hope Township, Warren County, heading north on two-lane undivided Union Street. The road passes homes before reaching the CR 611 junction and becomes Hope-Blairstown Road, running through wooded areas with some farms and homes. The route reaches an interchange with I-80 and winds north through more rural areas, coming to a junction with CR 608. CR 521 enters Blairstown Township and crosses over the abandoned Lackawanna Cutoff railroad line near the Blairstown station. Further north, the route intersects CR 607 before reaching the Route 94 junction and turns west to form a concurrency with that route. The road crosses Paulins Kill and comes into the community of Blairstown, where CR 521 splits from Route 94 at an intersection with CR 602. At this point, CR 521 heads northeast on Stillwater Road, passing a few businesses. The route enters wooded residential areas before coming into Hardwick Township at the CR 601 intersection. In Hardwick Township, the road heads through a mix of farms, woods, and homes, crossing CR 659 and passing near White Lake. CR 521 crosses into Stillwater Township, Sussex County, at which point the name changes to Maple Avenue.The road continues through rural areas as it reaches the residential community of Stillwater, where at the CR 610 intersection CR 521 makes a left turn onto Stillwater Road to continue northeast, reaching the CR 617 junction. The road turns more north as it heads back into rural surroundings and makes a right turn to the east, intersecting CR 612. In this area, the route passes through dense forests with a few homes and runs northeast along the western short of Swartswood Lake, which is contained within Swartswood State Park. Past the lake, CR 521 has an intersection with CR 622 and crosses into Hampton Township, where there