Rahway is located in southern Union County on the Rahway River, about 15 miles southwest of Manhattan. It is situated between the Garden State Parkway and the New Jersey Turnpike. According to tradition, Rahway was named after Rahwack, a local Native American tribal chief. European settlement dates to 1665. The community grew thanks to its location on the river and the major stagecoach road between New York and Philadelphia.
Growth accelerated after the arrival of the New Jersey Railroad in 1835. Carriage making became the leading industry, leading to the moniker Carriage Capital of the World. Incorporation as a city came in 1858. Location on the railroad spurred the development of many industries. The most important was Merck & Company, which moved to Rahway in 1903 and has since become a leader in pharmaceuticals.