Next, the route meets PA Route 221, and the two overlap for just over a mile, heading northwest through the village of Prosperity. After the village, Route 18 leaves the concurrency and heads northward through the villages of Van Buren, Lagonda, and Gabby Heights as it approaches the city of Washington nearly  later. In Washington, Route 18 briefly overlaps with US 40, and the routes head west, intersect with the western terminus of PA Route 136, and then turn northwest.
Following that, Route 18 intersects with PA Route 221 for about a mile before heading northwest through Prosperity. After the village, Route 18 diverges from the concurrency and travels northward through Van Buren, Lagonda, and Gabby Heights toward Washington. In Washington, Route 18 briefly overlaps with US 40 as it approaches the city, then turns west to intersect PA Route 136 before turning northwest.