The Ligget's Gap Railroad (originally incorporated on April 7, 1832) changed its name to the Lackawanna & Western Railroad on April 14, 1851. They then began obtaining track rights through the northern and western areas of New York on the New York & Eire Railroad and the Cayuga & Susquehanna Railroad. On December 4, 1850, Delaware & Cobb's Gap Railroad was chartered to build a line between Scranton, Pennsylvania and the Delaware River. Before the route opened, Delaware & Cobb's Gap and Lackawanna & Western merged, forming the Delaware, Lackawanna & Western (DL&W) Railroad on March 11, 1853. During the 1880s, DL&W added several new extensions and acquired the New York, Lackawanna & Western Railroad, which allowed them to offer a New York-Buffalo trunk line.

In the 1880s, DL&W also began using anthracite, which burned cleaner than the previous types of coal. These new, cleaner anthracite trains introduced the famous advertisements of Phoebe Snow. She became a model of the new woman who traveled independently and remained a popular image for nearly 70 years. In the early 1900s, DL&W rerouted and straightened its mainlines, which required high embankments and massive bridges. As part of the modernization of their lines, DL&W began the Clark's Summit-Hallstead Cutoff. The 39.6 mile project shortened the distance between Clark's Summit and Hallstead by 3.6 miles, reduced the grade and produced a straight line that saved a freight train as much as an hour and a passenger train at least ten minutes.

In order to construct the Clark's Summit-Hallstead Cutoff, DL&W had to build two massive viaducts, which were designed by Abraham Burton Cohen. Named after the creek it crossed, the Tunkhannock Viaduct remains the largest reinforced concrete structure built in the North Americirca Located in Nicholson, Pennsylvania, its total length is 2375 feet, it is two tracks wide, and has ten 180 foot arches and two 100 foot arches. All thirteen piers were sunk to bedrock, some resting 95 to 138 feet below the ground. Therefore, almost half of the bulk of the bridge is hidden underground. The viaduct required 167,000 cubic yards of concrete and 1140 tons of steel to build it. The main construction tool was a 3,028 foot, twin-line cable way. Timber towers at each end of the viaduct-one 150 feet high and the other 165 feet high-and a 240 feet high center tower supported the two cable cars. Each cable car could support a ten ton load of steel falsework, wooden forms, concrete or other construction material for the piers and arches. There were four cable spans and each was operated by separate engines. The Martin Creek Viaduct, located nine miles north of the Tunkhannock in Kingsley, Pennsylvania, is 1600 feet long and has 150 feet high arches, and used similar construction methods. The project began in 1912 and was completed in 1915, with the total cost of construction between 12 -14 million dollars. The bridges are still in use and the line is currently being run by Canadian Pacific Railway trains, is maintained and actively moving freight. Residents of Nicholson, Pennsylvania celebrate "Nicholson Bridge Day" annually.