This list include very varied financial entities. From completely defunct companies, to operating companies with operations turned into investments, some hanging onto a corporate skeleton owning properties as holding companies, or have assigned their properties in mergers, bankruptcy or other legal acts (dissolution of the corporation) and finally others having become extinct—their works either torn up and hopefully recycled, or sold off to operating companies. This list does not indicate which is which.  

The Lehigh and Hudson River Railway (L&HR) was the smallest of the six railroads that were merged into Conrail in 1976.

The Lehigh Valley Railroad (reporting mark LV) was a railroad built in the Northeastern United States to haul anthracite coal from the Coal Region in Pennsylvania.

The Louisville and Nashville Railroad (reporting mark LN), commonly called the L&N, was a Class I railroad that operated freight and passenger services in the southeast United States.

The Michigan Central railroad was created primarily by Boston capitalists for the purpose of purchasing the "Central" line from the State of Michigan. See "Central" line. In the late 1830's, the state had invested in several public works projects consisting of new railroads and canals. The "central" project was one of these. Though more successful than the other public works projects, the state decided to exit these projects and this line, radiating west from Detroit was sold to the Michigan Central.

The Minneapolis & St. Louis Railway was created on May 26, 1870 by a group of Minnesota investors interested in establishing a railroad connection between Minneapolis and the agricultural regions to the south. Minneapolis was home to the largest flour milling operations in the country at that time. Wheat was the primary commodity grown in southern Minnesota and Northern Iowa.

In 1867, Cornelius Vanderbilt acquired control of the Albany to Buffalo-running NYC, with the help of maneuverings related to the Hudson River Bridge in Albany. On November 1, 1869, he merged the NYC with his Hudson River Railroad to form the New York Central and Hudson River Railroad. This extended the system south from Albany along the east bank of the Hudson River to New York City, with the leased Troy and Greenbush Railroad running from Albany north to Troy.

Albany industrialist and Mohawk Valley Railroad owner Erastus Corning managed to unite the Albany and Schenectady Railroad, the Utica and Schenectady Railroad, the Syracuse and Utica Railroad, the Auburn and Syracuse Railroad, the Buffalo and Rochester Railroad, the  Schenectady and Troy Railroad, the L

The New York, Chicago and St. Louis Railroad (reporting mark NKP), abbreviated NYC&St.L, was a railroad that operated in the mid-central United States.

The Hartford and New Haven merged with the New York and New Haven Railroad in 1872, forming the New York, New Haven and Hartford Railroad (the New Haven). For the next 90 years, the route remained a vital passenger and freight route for the New Haven, with continuous passenger service even as most other lines in the region gradually had passenger service discontinued from the 1920s onward.

Wikipedia

The Norfolk and Western Railway (reporting mark NW),[1] commonly called the N&W, was a US class I railroad, formed by more than 200 railroad mergers between 1838 and 1982.

The Northern Central Railway (NCRY) was a Class I Railroad connecting Baltimore, Maryland with Sunbury, Pennsylvania, along the Susquehanna River. Completed in 1858, the line came under the control of the Pennsylvania Railroad (PRR) in 1861, when the PRR acquired a controlling interest in the Northern Central's stock to compete with the rival Baltimore and Ohio Railroad (B&O).

The Northern Pacific Railway (reporting mark NP) was a transcontinental railroad that operated across the northern tier of the western United States, from Minnesota to the Pacific Northwest.

An anecdote found in Day By Day for March 4, 1906:

Mark Twain Got the Stateroom.

The Pere Marquette Railroad was incorporated on November 1, 1899, in anticipation of a merger of three Michigan-based railroad companies[1] that had been agreed upon by all parties. It began operations on January 1, 1900, absorbing the following companies:

The Philadelphia and Reading Railroad (P&R) was one of the first railroads in the United States. Along with the Little Schuylkill, a horse-drawn railroad in the Schuylkill River Valley, it formed the earliest components of what became the Reading Company.

The Pittsburgh, Cincinnati, Chicago and St. Louis Railroad, commonly called the Pan Handle Route (Panhandle Route in later days), was a railroad that was part of the Pennsylvania Railroad system.

The Syracuse, Binghamton and New York is a corporation of the State of New York, having its principal office at New York, N. Y. While the present name of this company is that given above it was incorporated originally as the Syracuse and Southern Railroad Company, which was later changed to the present name of Syracuse, Binghamton and New York Railroad Company.

It is controlled by the Lackawanna through ownership of a majority of its outstanding capital stock. On the other hand, the records do not indicate that this company controls any common-carrier corporation.

The Toledo, Peoria & Western Railway was incorporated in Illinois on March 28, 1887, and consolidated the operation of the Toledo, Peoria & Warsaw Railway and the Logansport, Peoria & Burlington Railroad. The LP&B built from Galesburg to East Burlington, Illinois in 1855, and reached Gilman, Illinois in 1857 and Effner in 1859.

Wikipedia

The Western Maryland Railway (reporting mark WM) was an American Class I railroad (1852–1983) which operated in MarylandWest Virginia, and Pennsylvania.