Interstate 99 exists in two segments in Pennsylvania: an original 85-mile segment between the Pennsylvania Turnpike in Bedford and Interstate 80 in Bellefonte, by way of Altoona and State College, designated in stages between 1998 and 2008 and entirely concurrent with U.S. Route 220, and a northern 76-mile segment overlapping with U.S. Route 15 from Williamsport to the New York state line. Written into law rather than assigned by AASHTO, its numbering does not follow traditional Interstate highway numbering patterns, as the I-99 designation would be more sensible along the Atlantic coast.