Blawnox is a borough in Allegheny County about 9 miles east up the Allegheny River from Pittsburgh. The history of Blawnox is unique. It got its name from the Blaw-Knox Company which had a manufacturing plant in present day Blawnox. The plant took care of most of the town’s employment. Believe it or not, Blawnox was founded in the last 18th century and was called Hoboken. Steel was the neighborhood’s most popular industry, hosing the Blaw Steel Co. and the Knox Welded and Pressed Steel Co. Blaw Steel acquired Knox Welded and Pressed Steel Co. in 1917 and the two merged as the Blawknox Steel Construction Company. Blawnox was incorporated from O’Hara Township in April 1925.

Blawnox was incorporated on April 13, 1925, from O'Hara Township.

Blawnox is entirely surrounded by land to the north, northeast and west by the westernmost section of O'Hara Township. Across the Allegheny River, Blawnox runs adjacent with Penn Hills.