The corporate history of the Pennsylvania Railroad (PRR) in New York State is complex and sometimes confusing. It is made more challenging by the habit of some railroad companies to change names frequently or to create companies that only exist for a few months before being reorganized, sold, or merged. The tree below shows the companies that became part of the PRR in New York State.
- Pennsylvania Railroad (???? – 1968) and predecessors, including
- Northern Central Railroad (1861 – 1968)
- Williamsport and Elmira Railroad ( ? – 1863)
- Elmira and Lake Ontario (1886 -1956)
- Sodus Bay and Southern Railroad (1882 – 1886)
- Lake Ontario Southern Railway (1879 – 1882)
- Geneva, Hornellsville and Pine Creek Railway ( ? – 1879)
- Ontario Southern Railroad (1875 – 1879)
- Sodus Bay and Southern Railroad (1873 – 1875)
- Lake Ontario Southern Railway (1879 – 1882)
- Elmira, Jefferson and Canandaigua Rail Road
- Elmira, Canandaigua and Niagara Falls Rail Road (1857 – 1859)
- Canandaigua and Elmira Rail Road (1852 – 1857)
- Canandaigua and Corning Railroad (1845 – 1852)
- Canandaigua and Elmira Rail Road (1852 – 1857)
- Elmira, Canandaigua and Niagara Falls Rail Road (1857 – 1859)
- Chemung Railroad (1845 – 1886)
- Canandaigua Lake Railroad (1887 – 1888)
- Sodus Bay and Southern Railroad (1882 – 1886)
- Western New York and Pennsylvania Railroad (1887 – 1895) / Railway (1895 – 1917)
- Buffalo, New York and Philadelphia Railway (1871 – 1883) / Railroad (1883 – 1887)
- Buffalo and Washington Railway
- Genesee Valley Canal Railroad
- Rochester, New York and Pennsylvania Railroad (1881 – 1916)
- Olean, Bradford and Warren Railroad (1877 – 1898)
- Olean and Salamanca Railroad (1882 – 1883)
- Buffalo, Pittsburgh and Western Railroad (1881 – 1883)
- Buffalo, New York, and Pennsylvania Railroad
- Buffalo, Corry and Pittsburgh Railroad
- Buffalo and Oil Creek Cross Cut Railroad
- Salamanca, Bradford and Alleghany
- Titusville and Oil City
- McKean and Buffalo Railroad (1874 – 1911)
- Union Terminal Railroad Company of the City of Buffalo (1884 – 1917)
- Buffalo, New York and Philadelphia Railway (1871 – 1883) / Railroad (1883 – 1887)
- Northern Central Railroad (1861 – 1968)