Known as the Proud City of Proud People, the city of Arnold is located on the eastern shore of the Allegheny River, northeast of Pittsburgh. According to the United States Census Bureau, the city has a total area of 0.8 square miles (2.1 km²), of which 0.7 square miles (1.8 km²) is land and 0.1 square miles (0.26 km²) (6.41%) is water.

Present-day Westmoreland County was part of the hunting reserves of the Iroquois Indians. Americans began to penetrate the area in the 1750s, and circa 1781 Robert McCrea purchased the land on which Arnold is situated. William Jack acquired the property and later passed it on to Wilson Jack. The area around Arnold was first settled in 1852 by Indian fighter Major Andrew Arnold. It is from Major Andrew that the area derives its name. He later gave this land to his daughter, Sarah E., wife of Colonel Robert Parks Crawford. The land was just beginning to settle when the Chambers Glass Company became established in 1891. Arnold was part of New Kensington until it was separately incorporated as a borough in January 1896, and as a third-class city in 1939.

Arnold has a number of historic landmarks which help preserve its rich history.

Morris Davis

On the corner of Leishman and Richmond Avenue is the Morris Davis home. It was built by Morris Davis who had a major role in the political history of Arnold as a city councilman. It was one of the first homes in Arnold to have electricity.

Hartley Howard

This home stands midway in the 1600 block of Leishman Avenue. It was once the home of Harry Koessler, one of the early Burgesses of Arnold.

John Fedan

In 1917 John Fedan built this structure to be rented out to other merchants. When no one rented the office space, he started a hardware business for himself. He later added a furniture and appliance store.

Arnold Traffic Store

Another long time standing building in Arnold is what was once the Arnold Traffic Store, now home to Arnold Furniture. The building had been a general store, a meeting place, a temporary church for Arnold Presbyterians, an office for ALCOA, an amateur playhouse, a nightclub, and W.R. Gotts Furniture Store.

The Arnold Station

When the Allegheny Valley line extended its tracks, it laid a double line to Arnold and a single track continued on. At that time, a very unusual agreement was signed between the railroad company and W. H. Crawford that every train was required to stop and sign a registry. As a result, many trains came to a complete halt and the conductor would leave the train and reboard when passing through Arnold. The three daily express trains always stopped in Arnold, despite the fact that New Kensington was larger and more populous.