The library's roots go back to 1794 and the founding of the Norristown Library Company by 90 families residing in Lower Merion, Norriton, Plymouth, Providence, Whitemarsh, Whitpain, and Worcester townships. The library was formally incorporated in 1796. One of the signers of the Declaration of Independence, Pennsylvania Supreme Court Justice Thomas McKean, signed the charter issued in March 1796 that established the corporation.
Today, the Montgomery County - Norristown Public Library is a nonprofit corporation 501(c)(3) supported by appropriations from Montgomery County commissioners, municipal governments, and the Norristown Area School District. Additional income is derived from bequests, grants, gifts, fines, and fees.