 The area around Arnold was first settled in 1852 by Major Andrew Arnold, who grew up in Kittanning.With the creation of Westmoreland County in 1773, the area that became Arnold was originally part of Burrell, and later Lower Burrell, townships.Arnold was then part of the newly-created city of New Kensington from 1891 until it was separately incorporated as a borough in January 1896, and as a third-class city in 1939.