U.S. Route 15

Starting at US 17 Alt. in Walterboro, US 15 goes east, running parallel to Interstate 95 (I-95) and across I-26. Then it turns north and crosses I-95. Just before the town of Santee, US 15 converges with US 301. In Santee, the two highways merge with I-95 at exit 98 and all three cross Lake Marion. At exit 102, US 15/US 301 split off from I-95 and go into the town of Summerton. US 15 then separates from US 301 and heads mainly north to city of Sumter. From there, it continues north, crosses I-20, and goes through the cities of Bishopville and Hartsville to the town of Society Hill. It is here that US 401 joins US 15 and both go to the North Carolina border.

James Taylor Bridge, Chapel Hill, North Carolina, part of the US 15/US 501 route

US 15/US 401 continues to Laurinburg, at which US 401 splits off and US 15 runs concurrent with US 501. US 1 briefly merges with US 15/US 501 through Aberdeen and Sanford. The route continues north of Sanford with North Carolina Highway 87 toward Pittsboro. Past Pittsboro, US 15/US 501 goes toward Chapel Hill and skirts around the southeastern edge of the city and then across I-40 to Durham. (Prior to the construction of the Chapel Hill bypass, US 15 ran through Chapel Hill, and, as of 2018, there is a "Jefferson Davis Highway" marker on Franklin Street, Chapel Hill's main street.[2]) Here, US 15 Business (US 15 Bus.)/US 501 Bus. split from US 15/US 501. Before the business routes rejoin on the other side of Durham, I-85 merges into US 15 Bus. Then, I-85/US 15 go north. Right after crossing Falls Lake at exit 186, US 15 splits off to the east. US 15 runs parallel to I-85, going through the city of Creedmoor. It then crosses back over I-85, goes through the city of Oxford, on through Bullock, and then to the North Carolina–Virginia state line.

View north along US 15 north of SR 230 in Madison Mills, Virginia

Virginia's section of US 15 starts in Mecklenburg County. Not far from the state line, it crosses a narrow finger of Kerr Lake. The highway goes through the town of Clarksville and merges very briefly with US 58/State Route 49 (SR 49) and then crosses over the main body of Kerr Lake. US 15 continues a little ways and merges with US 360. The two highways go on to the town of Keysville. After Keysville, US 15 branches off and goes to the town of Farmville. After a brief merge with US 460, US 15 goes through the towns of Dillwyn, New Canton (on the James River), Fork Union, and Palmyra before crossing I-64 at Zion Crossroads. After passing the Interstate, US 15 goes through the towns of Gordonsville (with a quick merge with US 33) and Orange, and then on to Culpeper. After Culpeper, US 15 runs concurrent with US 29. In Warrenton, they briefly merge with US 17. South of Gainesville, US 15 breaks off and crosses I-66. From there, it goes on to Leesburg and then to the state line.

US 15 starts in Maryland at Point of Rocks, crossing the Potomac River and then merges into US 340 just south of Frederick. In Frederick, US 40 merges with US 15 for a very short distance. From there, US 15 goes through Thurmont and on to the Maryland–Pennsylvania border.

"Future I-99 Corridor" sign on US 15 southbound north of Williamsport, Pennsylvania

Authentic US 15 shield at the former northern terminus in Rochester, New York

US 15 enters Pennsylvania south of Gettysburg. US 15 Bus. (Emmitsburg Road) goes through Gettysburg, while US 15 bypasses the borough; the bypass continues to York Springs. US 15 passes through Dillsburg before becoming a freeway near Grantham and the Messiah University campus.

US 15 continues as a freeway until it intersects US 11 and Pennsylvania Route 581 in Camp Hill. US 15 runs concurrent with US 11, passing Harrisburg on the west shore of the Susquehanna River. The concurrency ends at Shamokin Dam, where US 11 splits and follows the North Branch Susquehanna River, and US 15 follows the West Branch Susquehanna River north toward Williamsport where it passes through Lewisburg and the campus of Bucknell University (which is partially bisected by the highway). In the future, US 15 and US 11 will diverge in Selinsgrove, from which US 15 will proceed north on a road yet to be built and connect back to its current alignment near Winfield. US 11 will be joined to a business loop of US 15 instead of the main route.

The segment from Williamsport, Pennsylvania, to the northern terminus at I-86 and NY 17 in Painted Post, New York, has been completely upgraded to Interstate standards, except for one access road at milemarker 150.1, in preparation for the eventual transition to designation as I-99, as has the US 15/I-86 interchange. The 12.59-mile (20.26 km) segment of US 15 in New York runs parallel to the Tioga River from the state line to its current northern terminus at I-86 and NY 17 exit 44 at the junction of the Tioga and Cohocton rivers in Painted Post, west of downtown Corning. The entire length of US 15 in New York is signed concurrently with I-99.