Rensselaer, a city of Rensselaer county, New York, U.S.A., in the eastern part of the state, on the E. bank of the Hudson river, opposite Albany. Pop. (1900) 7466, of whom 1089 were foreign-born; (1910 census) 10,711. It is served by the New York Central and the Boston & Albany railways, which have shops here, and is connected with Albany by three bridges across the Hudson. Rensselaer, originally called Greenbush, was first settled in 1631, and the site formed part of the large tract bought from the Indians by the agents of Killian van Rensselaer and known as Rensselaerwyck. In 1810 a square mile of land within the present city limits was acquired by a land speculator, was divided into lots and offered for sale. Development followed, and five years later the village was incorporated. In 1897 Greenbush was chartered as a city, and its name was changed to Rensselaer. Its limits were extended in 1902 by the annexation of the village of Bath (pop. in 1900, 2504) and the western part of the township of East Greenbush. Rensselaer manufactures knit-goods, wool shoddy, felt, &c.