While the current road runs from Bedford past Bald Eagle to Port Matilda, Pennsylvania, future plans have this road starting from the Pennsylvania-Maryland border mostly along U.S. Route 220 and then continuing northward along U.S. Route 15 towards the New York state line. Current plans have this road ending at Interstate 80 near Bellefonte.
The names given to this road include the Bud Shuster Highway and Appalachian Thruway; the latter name continues north with US 220 and US 15.
Within Pennsylvania, the road ran 51.2 miles (82.4 km), all concurrent with U.S. Route 220, from an indirect connection with the Pennsylvania Turnpike (Interstate 70 and Interstate 76) near Bedford north past Altoona to a temporary terminus at U.S. Route 322. Immediate plans will extend it northeast past State College to Interstate 80 near Bellefonte.
Bedford to Altoona
Interstate 99 currently begins as a continuation of the two lane portion of U.S. Route 220 from Maryland near the Pennsylvania Turnpike (I-76). The interchange with the turnpike requires drivers to get onto Old U.S. Route 220 near Bedford in order to connect to the Pennsylvania Turnpike.
This route continues north towards Altoona.
Altoona to Port Matilda
From Altoona, the highway has a large intersection with U.S. Route 22 in Hollidaysburg. This interchange allows travellers to head west towards Ebensburg and Johnstown. Pennsylvania Route 764 intersects further at Bellwood.
Northward towards Tyrone, Interstate 99 runs along one of the older sections of the highways when U.S. Route 220 was first converted to a limited access highway.
In Tyrone itself, Interstate 99 is a short elevated expressway at Pennsylvania Route 453. This section is notorious for speed traps as many cars heading downhill from Bald Eagle must brake in order to stay within the speed limit.
Until the end of 2007, the highway ended north of Tyrone at the village of Bald Eagle, where traffic was diverted on to U.S. Route 220. On December 22, 2007, after several long construction delays, the section from Bald Eagle to Port Matilda was opened to traffic. Northbound traffic is currently diverted to U.S. Route 322 eastbound, locally known as Sky Top Mountain Road, north of Port Matilda at the crest of Bald Eagle Mountain. Southbound traffic can enter the highway one exit further south, from U.S. Route 322 eastbound at Port Matilda. The southbound lanes in the section between these two exits remains closed for the remediation of the acidic rock.