Interstate 99

Interstate 99 (I-99) is an Interstate Highway with two segments: one located in central Pennsylvania, and the other in southern New York in the United States. The southern terminus of the route is at exit 146 of the Pennsylvania Turnpike (I-70 and I-76) north of Bedford, where the road continues south as U.S. Route 220 (US 220). The northern terminus of the Pennsylvania segment is at I-80 near Bellefonte. The New York segment follows US 15 from the Pennsylvania–New York border to an interchange with I-86 in Corning. I-99 passes through Altoona and State College—the latter home to Pennsylvania State University—and is entirely concurrent to US 220, within Pennsylvania. Long-term plans call for I-99 to be extended southward along the US 220 corridor to an interchange with I-68 in Cumberland, Maryland.

Unlike most Interstate Highway numbers, which were assigned by the American Association of State Highway and Transportation Officials (AASHTO) to fit into a grid, I-99's number was written into Section 332 of the National Highway System Designation Act of 1995 by Bud Shuster, then-chair of the U.S. House Committee on Transportation and Infrastructure, the bill's sponsor, and the representative of the district through which the highway runs. I-99 violates the AASHTO numbering convention associated with Interstate Highways, since it lies east of I-79 but west of I-81.