Mountainside is a borough in Union County, New Jersey, set on a ridge within the Raritan Valley and Rahway Valley regions of the New York metropolitan area. With a population of roughly 7,000, it is a predominantly residential community known for larger lots, strict zoning, and an unusually strong connection to preserved open space. The borough sits directly against the Watchung Reservation, a forested preserve of more than 2,000 acres that functions as the community's natural centerpiece. The Watchung Reservation shapes daily life in Mountainside. Its hiking and bridle trails, Lake Surprise, and the Trailside Nature and Science Center with its planetarium are located at or near the borough's edge, making the reservation both a recreational amenity and a defining element of the town's identity. Echo Lake Park, with its two lakes and popular walking loop, extends the outdoor options further and draws walkers, runners, and cyclists throughout the year. Mountainside operates its own K-8 school system, anchored by Deerfield School, and sends high school students to Governor Livingston High School in neighboring Berkeley Heights, a regional sending arrangement that is a well-known draw for families. The borough also runs its own community pool and a full slate of recreation programs based near Borough Hall. The borough's residential character is one of space and calm, with a suburban, nature-oriented feel that contrasts with the density of nearby cities. Everyday shopping and dining are reached along Route 22 or in the surrounding communities of Westfield, Summit, and Berkeley Heights. Transportation is oriented around Route 22, which crosses the borough and carries commuter bus service into the Port Authority in Manhattan, while train stations in nearby Garwood and Westfield provide rail access. Newark Liberty International Airport is a short drive away. Mountainside suits those seeking a quiet, green suburban setting with established schools and manageable access to New York City.