The Union Railroad is part of the original Lake Erie to Pittsburgh Mills rail system that had its beginning in 1896. During 1897, the URR handled approximately 5 million tons of freight. The tonnage increased through the years, until a peak was reached in 1951, when an all-time high of 74,44O,776 net tons of revenue freight were handled.

This Class III switching railroad is engaged in general railroad transportation and provides railroad switching service primarily to the steel industry.In addition to steel mills, the railroad serves the coal industry through Duquesne Wharf, a world class coke production facility at Clairton, and more than 30 other customers in the automotive, chemical, and aggregate business. The URR currently consists of 65 miles of main track and approximately 200 miles of yard tracks and sidings, all located within a 10-mile radius in Allegheny County, PA. The northernmost point is located at North Bessemer, PA, where the railroad proceeds southward through Turtle Creek, East Pittsburgh, Monongahela Junction, Clairton Junction and Clairton.

The railroad, as it exists today, has resulted from the union of all or parts of five railroads between the years 1906 and 1915. The first addition occurred in 1906 when a portion of the Pittsburgh, Bessemer and Lake Erie Railroad, extending from North Bessemer to East Pittsburgh, was leased to the Union Railroad. Later in 1906, the railroad leased the Monongahela Southern Railroad. The next addition involved the St. Clair Terminal Railroad in 1920. All three properties were subsequently merged. The last addition occurred in 1915 with the lease of track from Duquesne to McKeesport via the Penn Central Bridge. The original URR extended from East Pittsburgh to Hays, a distance of six miles, and was constructed in the years 1894-1907. During the same period, 13 branches, with an aggregate length of 14 miles were built. Operations began on June 1, 1896, with 241 employees, 25 steam locomotives and no cars. On October 26, 1897, the first train was interchanged with the Pittsburgh, Bessemer & Lake Erie Railroad at East Pittsburgh. This 30-car ore train from North Bessemer was consigned to Edgar Thomson.

The Port Perry Bridge, across the Monongahela River, opened to traffic on June 30, 1898. The Carrie Furnace bridge opened to hot metal traffic on December 31, 1900 and to general traffic on June 14, 1901. A new Homestead connection between Port Perry Bridge and the north end of Munhall Yard was completed and placed in operation December, 1907. This connection replaced the original line which was located along the hillside at Green Springs.

The Monongahela Southern Railroad extended from a point underneath the street railway bridge on Duquesne Boulevard, Duquesne, to Mifflin Junction. The railroad was placed in operation as it was built beginning in 1898. It was used for the disposition of hot slag and waste materials until June 17, 1906, when the first interchange of traffic occurred with the Wabash, Pittsburgh Terminal Railway. This railway was later known as the Pittsburgh and West Virginia Railway, until merged with the Norfolk-Western Railway. The Clairton Branch of the Monongahela Southern Railroad was constructed between the years 1917- 1920. It extended from Clairton Junction (Bull Run) to a connection with the St. Clair Terminal Railroad in Clairton and was first opened to operations on April 14, 1919. The St. Clair Terminal Railroad began at the connection with the Monongahela Southern Railroad in Clairton, and extended approximately 4- 1/2 miles to the end of the Clairton Steel Works, and to Wylie.

Major changes were made to the "J" Tower in 1930. These changes included the addition of the north and south Legs of the Duquesne Wye, the south Leg of the Homestead Wye, and the bridge over the then Pennsylvania Railroad tracks. In 1942, the six track Port Perry Yard spanning Turtle Creek was built to improve the availability of raw materials to Edgar Thomson Steel Works. The High and Low Grade Viaducts were completed in 1945. Turtle Creek Viaduct, on a new alignment, was opened to trains in 1951. These structures replaced the old viaducts which could not continue to support the ever-increasing size and weight of equipment and capacity carloads. In 1953 and 1954, a hump-operated Classification Yard and related facilities were constructed in Duquesne. The yard extends from Clairton Junction to the south approach to the Port Perry Bridge. The related facilities consist of a 9-track Receiving Yard and an 8-track Southbound Yard. On January I, 1960, an agreement was made with the B&O Railroad for joint use of their Tracks No. 4, 5, and 6 at Bessemer, located along the Port Perry Yard, at Union Junction, to provide adequate facilities for the delivery of ore to the dumper at Edgar Thomson Works. In addition, various track changes in the properties of the Union, B&O, and USS Corporation were made to further improve facilities. Major alterations and additions were made to Duquesne Coal Dock in 1964. Coal handling potential increased 250 tons per hour by the installation of a 15 cubic yard Bucyrus Erie revolving crane, a 4,800 cu. ft. storage bin, conveyor system, retarders and barge moving equipment. In 1978, the Coal Dock was further expanded to include a continuous bucket unloader.

In February, 1999, the URR replaced the Bucyrus Erie Revolving Crane with the largest bulk material crane on the Inland Waterway of the U.S. The new E-Crane, built by Indusign and Ohio Crane, will allow the Duquesne Wharf to enhance its tradition of providing reliable, high quality services to our customers and will improve Union Railroad's ability to competively handle coal and other bulk materials well into the 21st Century.

On January 7, 1966, a consolidated remote-controlled interlocking system was installed. This system, the first of its type in the industry, enables operating trains to make over a CTC (Centralized Traffic Control) system, utilizing a process control computer and a control machine. The control machine indicates track occupancy and train movement on a miniature track model of the entire main line. In this manner, all train movements are continually monitored by an operator and train movement director. In addition to tracking existing train movements, the computer selects preferential routines for new movements and positions power switches and signals.

In 1988, the Union Railroad became part of Transtar, Inc. Transtar is a privately-held transportation holding company with principal operations in railroad freight transportation, dock operations, and inland river barging. The Transtar subsidiary companies were formed over the years to meet the transportation needs of various steel making facilities that were the predecessors of today's United States Steel Corporation. Prior to 1988, the Transtar companies were wholly owned transportation subsidiaries of United States Steel Corporation. In December, 1988, these transportation companies were acquired by a new holding company, Transtar, Inc.

The Transtar companies have a long business history, more than 100 years in many cases. The companies provide a broad mix of specialized transportation services by rail and water. In addition, some of the rail and water carriers own and operate bulk commodity docks and port facilities. Transtar's core business is serving the transportation needs of the steel, utility, mining, and chemical industries, although other business supplements this core.