Portland Iron Works was founded in 1882 by Orlando Clarke and E. H. Thompson. A few years later, James A. Govanlock bought a share of the business and was active in the company until his death in 1903. Harry T. Clarke, son of Orlando Clarke, was president and manager from 1890-1918. In 1908, LeRoy Andersen joined the company as a stenographer, and in 1920, he became secretary and manager. In 1947, the Andersen family purchased Portland Iron Works from the Clarke family, making LeRoy Andersen the president. His son Lester Andersen served as president from 1969-1979; he was succeeded as president by Timothy Andersen, grandson of LeRoy Andersen.

The principal products of the plant were sawmill and transmission machinery, as well as floor and roof drains. In addition, they produced ripsaws, edgers, trimmers, steam engines, and castings for machinery. The company also contracted general iron work. During World War II, Portland Iron Works manufactured one-third of all the throttle valves used on Liberty ships.

Affiliated companies are Power Transmission Products, the General Bearing Company, Cascade Industrial Supply, the Paul Roberts Company, and the Fisher Brothers Company. Two other manufacturing divisions are PTP Machinery in Salem and PTP Hydraulics of Portland, manufacturer of hydraulic power units.