In Northeast Ohio, US 224 is always a short distance north of the Western Reserve's southern boundary.
Although U.S. 224 is only in Pennsylvania for a few short miles, the eastern terminus has changed several times since being issued in 1933, ending at various points in New Castle, Pennsylvania or in adjacent Union Township west of the city. The eastern terminus has been moved five times (1936, 1947, 1974, 1977, 2008), the most notable of which was in the 1970's when the New Castle Bypass opened in 1974 and saw an extension of U.S. 224 through the city itself and into Shenango Township at the eastern terminus of the bypass, essentially taking over U.S. 422's old alignment after 422 moved to the bypass.
The route was truncated back at the current interchange with 422 and the current PA 60 (soon to be an extension of I-376) in 1977 while the old alignment through New Castle was replaced by Business 422. This would be the case until March 20, 2008, when 224 was officially extended two miles to PA 18 inside the New Castle city limits with the placement of new signs. PennDOT had gotten approval from the AASHTO for the extension in September 2007.
The extension of U.S. 224 marked the second extension of a major highway into downtown New Castle in a little more than a year, as Pennsylvania Route 65 was extended a mile from its previous terminus with Business 422 to the PA 108/PA 168 concurrency in February 2007.