Between the western bank of the Delaware River and the Maryland Line, US 1 pursues a southwesterly course across the undulating terrain of Bucks County, through the city of Philadelphia, and over the section of the highway known as the Baltimore Pike. The highway crosses the Delaware River on the TRENTON- MORRISVILLE BRIDGE at a point where in 1804 the first bridge across the Delaware was built.Bucks County was established in 1682 by William Penn as one of the three original counties. The rolling surface and fertile soil of the county are adapted to agriculture, the chief occupation of the in- habitants; small farms predominate. At the Pennsylvania-Maryland State Line, the MASON-DIXON LINE, was surveyed and marked by Charles Mason and Jeremiah Dixon,Englishastronomers,in1763-67.These men had been commissioned by the Penns and the Calverts to determine the boundary in order to settle disputes among claimants of land under various grants dating back to 1682. George Calvert, Lord Baltimore, founder of Maryland, under his grant claimed a part of Pennsylvania that would have included the site of Philadelphia as far N. as the Holmesburg section. This dispute was adjusted in 1738 and a boun- darylinewasestablished15milesbelowPhiladelphia. Laterthepresent line was run, Mason and Dixon placing stone markers at 5 -mile intervals along a stretch of 132 miles. On the side facing Pennsylvania the letter P and the arms of the Penn family were carved; on the Maryland the crest of the Galverts. The Mason- land side, the letter Dixon Line was generally accepted as the dividing line between the free and the slave States the North and the South.