Knox Law began in 1958 as a partnership among William W. Knox, Gerald J. Weber, Conrad A. Pearson, and John M. McLaughlin.
In 1964, Gerald J. Weber was appointed to the U.S. District Court for the Western District of Pennsylvania, the first of four members of the firm to become federal judges. William W. Knox joined him in 1970. Sean J. McLaughlin was appointed in 1994, stepping down in 2013 to become General Counsel of the Erie Insurance Group. He returned to the firm in 2019. A long-time firm leader and litigator became a Magistrate Judge for the Western District in 2018.
Mortimer E. Graham, who had been General Counsel of the Hammermill Paper Company, joined the firm in 1967. William C. Sennett was named Attorney General of Pennsylvania in the same year, returning to the firm in 1970. The firm became a professional corporation in 1971, one of the first in Pennsylvania.
Jackson D. Magenau and M. Fletcher Gornall merged their four-member practice into the firm in 1976. The firm soon began construction of the first freestanding law office building in downtown Erie. Expansion of the building was necessary within a decade.
Richard H. Zamboldi and Richard W. Perhacs joined the firm laterally in 1990. Other experienced local attorneys followed. In 2007, the firm opened an office in Jamestown, New York. The firm established a presence in North East, Pennsylvania, in 2009, when James S. Bryan brought a third-generation practice to the firm. Robert J. Jeffery joined the firm in 2018, bringing another distinguished North East practice (Orton & Jeffery, P.C.). In 2018, the firm opened an office in Pittsburgh.