 US 29 / 15 is joined by US 17 south of Warrenton in Fauquier County, and continues around the town, with US 17 splitting off.US 29/15 continues mostly eastward to Gainesville where US 15 splits and US 29 intersects Interstate 66 for the first time.US 29 continues into Fairfax County, where it passes along the boundary of the city of Falls Church, where the road has two different names.