U.S. Route 22 in Pennsylvania

US 22 eastbound at the PA 145 interchange in Whitehall Township

The Lehigh Valley Thruway is a 24-mile-long (39 km) freeway portion of US 22 from the eastern end of the Interstate 78/US 22 concurrency in Kuhnsville, west of Allentown, to the state line in Easton. The highway travels just to the north of Allentown and Bethlehem and passes through Easton.

Originally, I-78 would have continued with the U.S. 22 concurrency on the Lehigh Valley Thruway into New Jersey, and I-178 and I-378 serving Allentown and Bethlehem respectively. Due to opposition in Phillipsburg, New Jersey on the building of a new highway through the town, PennDOT and NJDOT decided to reroute I-78 to the south and allow U.S. 22 to remain on the limited-access highway, which, after going through a series of sharp, potentially dangerous curves in Easton and crossing the Delaware River into New Jersey, becomes an at-grade divided highway in Phillipsburg.

Traffic on the Lehigh Valley Thruway is often heavy at rush hour, particularly near the PA 145 interchange. The series of sharp curves is locally known as "Cemetery Curve", and because of it, the speed limit is lowered to 45 mph at Route 248 and then lowered to 35 mph around the sharpest part of the curves. At the interchange with Bushkill Street, US 22 becomes an elevated highway until crossing into New Jersey. The speed limit drops once again to 25 mph while crossing the Easton–Phillipsburg Toll Bridge.

The first alignment of the William Penn Highway became problematic for motorists in Lebanon along the current U.S. Route 422; Reading via U.S. Routes 22 and 222 and Allentown on Hamilton Street (present-day PA 222).[5] The highway continued through Allentown on Hanover Avenue and through Bethlehem on Broad Street, Linden Street, and Easton Avenue.

Pennsylvania Route 43 was aligned as a bypass, north of the Pennsylvania Dutch Country, that ran from U.S. Route 22, U.S. Route 11, and Pennsylvania Route 5 in Harrisburg to Pennsylvania Route 12 in Bethlehem.[6] From Harrisburg, this route followed modern-day US 22 to Paxtonia, then Jonestown Road to Jonestown and modern-day Old Route 22, Airport Road, and Main Street through Fredericksburg. East of here to Fogelsville, the route is variously called Old Route 22, Shartlesville Road, and Hex Highway. The route from Fogelsville to the Allentown line, now Main Street and Tilghman Street, was designated LR 443 in 1925[7] before being incorporated into this route.[8] The route entered Harrisburg by Liberty Street and connected with the William Penn Highway through 17th Street. The New York Times was recommending use of this cutoff by early 1931.[8] On June 8, 1931, the American Association of State Highway Officials came to a resolution for the traffic problem, by replacing the PA 43 corridor with US 22. The Pennsylvania Department of Highways moved the William Penn Highway name to match.[4][5] The state deleted a concurrency with PA 43 and what was then US 309 and truncated PA 43 to Susquehanna Street and Broadway from Allentown to Bethlehem.[9] Signs were changed to reflect the new designations on May 31, 1932, with the new route designations officially in place on June 1, 1932.[10]

Tilghman Street was eventually connected directly from Cetronia to Allentown by a bridge over Cedar Creek; Tilghman Street (west of the Lehigh River) and Union Boulevard (east of the river) were joined in 1929 by a bridge. By 1936, US 22 had been moved from its Hamilton Street and Broad Street alignment to Tilghman Street and Union Boulevard through Allentown and Bethlehem. From Bethlehem to Easton, an alternate route was formed along Goepp Street, Pembroke Road, and Freemansburg Avenue. With the construction of a new bridge over the Delaware River in 1938, Prospect Avenue, Pearl Street, and Snyder Street in Easton were incorporated into US 22.[11] A new alignment from Fredericksburg to Paxtonia was built in the early 1940s.[12] When the Lehigh Valley Thruway was completed in 1954, US 22 was moved onto it; its old alignment was redesignated State Route 1002 through Lehigh County. With the completion of Interstate 78, US 22 was moved onto that highway from Fredericksburg to Kuhnsville. The former alignment, although no longer a major state highway, is still well traveled by those who live in the vicinity.

The origins of this section of US 22 date back to the early 1800s, with the chartering of the Harrisburg, Lewistown, Huntingdon and Pittsburgh Turnpike in 1807, following the course of what would become US 22 from Harrisburg to Pittsburgh,[13] providing a more northerly alternative to the Harrisburg and Pittsburgh Turnpike chartered the year prior. Support for the turnpike was lacking along its route, and so to foster a sense of locality to the road the company was broken up in the subsequent years into five sections: the Huntingdon, Cambria, and Indiana in 1810 (terminating at Huntingdon and Blairsville); the New Alexandria and Conemaugh in 1816 (Blairsville to New Alexandria); the Pittsburgh and New Alexandria Turnpike in 1816; and the Harrisburg and Millerstown, Millerstown and Lewistown, and Lewistown and Huntingdon Turnpikes in 1821. In their own times, these companies constructed a highway across the Appalachians collectively called the Northern Pike, but all folded with competition from the Main Line of Public Works, and later the Pennsylvania Railroad.

In its earliest years, US 22 deviated from the original course of the William Penn Highway in a few notable places. With the construction of the Boulevard of the Allies in the early 1920s, the highway was rerouted to service this thoroughfare. This alignment entered Pittsburgh on modern day Route 8, then made its way downtown by Dallas Ave, Wilkins Ave, Beeler Street, Forbes Street, the Boulevard of the Allies, and Second Street. The highway then followed the old Pittsburgh and Steubenville Pike to Ohio. With the construction of the Penn-Lincoln Parkway in the late 1950s, both US 22 and US 30 were shifted to the new highway. Further east, where the William Penn Highway deviated from the Northern Pike between Ebensburg and Water Street to service Altoona and Tyrone, the Northern Pike was restored as the main east–west thoroughfare, while US 220 was chosen to service these cities. A few notable deviations from this include Turkey Valley Road near Canoe Creek Lake, and a bend servicing Williamsburg via modern-day PA 866 and SR 2015, which both deviated from the Northern Pike.[14] These were later christened as PA 303 and PA 203 respectively when the highway was restored to the Northern Pike.[6] Near the Susquehanna River, before an alignment along the Juniata River had been constructed, the highway serviced New Bloomfield and Meck's Corner by modern-day PA 34 and PA 274; while US 22 was shifted north, this alignment still held its old designation of PA 3 for some time afterwards.[6]