Pennsylvania Power & Light Company. Predecessor and subsidiary companies. Local transit companies.

The development of electric distribution systems and workable traction motors led to widespread construction of trolley networks in the 1890s. Many systems began as electrifications of the horse car lines that had appeared in major cities starting in the 1850s and spread to county seats and other large rural towns over the next twenty years. Electric traction made possible the construction of light interurban rail lines linking cities and their outlying villages. Such transit systems were cheaper to build and operate than steam railroads.

As traction systems were large consumers of electricity and required electric distribution networks along their lines, they were amalgamated with electric power companies at an early date. Ultimately, the large electric holding companies that emerged in the first two decades of the 20th century acquired near-monopolies of electric traction as well as electric power and distribution and sales within their respective territories.

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