The route crosses South Mountain into Cumberland County and reaches Mount Holly Springs, where it intersects PA 94.

PA 34 crosses into Cumberland Township and becomes Biglerville Road, passing through fields within Gettysburg National Military Park.

The route heads into Butler Township and crosses the Gettysburg and Northern Railroad as it passes through a mix of farms and woods with some homes.

The route enters Menallen Township and runs through Floradale prior to curving to the northeast through more agricultural areas with some patches of woods and homes.

The route crosses the Bermudian Creek into Huntington Township and runs through Idaville before heading through more areas of farms, woods, and residences.

[2][3] PA 34 crosses into Dickinson Township in Cumberland County and runs through more agricultural areas with some homes, passing through Goodyear.

The route heads into the borough of Mount Holly Springs and becomes Yates Street, running through wooded areas of homes before intersecting the northern terminus of PA 94.

The route widens into a four-lane divided highway and fully enters Carlisle as it interchanges with I-81 in a commercial area.

The route crosses into North Middleton Township and passes under I-76 (Pennsylvania Turnpike), becoming Spring Road and curving northeast past a few businesses.

PA 34 runs northeast through open farmland before entering wooded areas of homes, at which point the route ascends forested Blue Mountain.

[2][4] PA 34 heads into Carroll Township in Perry County, where it descends Blue Mountain and passes a few homes.

The road turns north and crosses Little Mountain before coming into a mix of farms and woods with some residential and commercial development.

The road heads into Centre Township and winds northwest through farms, woods, and residences before coming into the borough of New Bloomfield.

PA 34/PA 274 turns north onto South Carlisle Street and passes homes before coming to a traffic circle the center of town.

[2][5] The route turns northeast and heads back into Centre Township, becoming Keystone Way and passes through agricultural areas with some homes.

Here, PA 34 curves north across forested Limestone Ridge prior to heading northeast again and passing through farmland and woodland with some homes and businesses.

The route passes under Norfolk Southern's Pittsburgh Line prior to crossing the Juniata River into Howe Township.

PA 34 curves south and then east to reach its northern terminus at US 11/US 15 just west of the Millersburg Ferry across the Susquehanna River.