then turns southeast for a few miles, passing through Newtown Township, Delaware County and entering Radnor Township, where it receives its first two named tributaries, Thomas Run and Little Darby Creek, from the right and left, respectively. The creek then turns south-southeast for several tenths of a mile before turning southeast for several more miles. In this reach, it receives the tributary Miles Run from the left and the tributary Camp Run from the right. The creek eventually turns east briefly before receiving the tributary Ithan Creek from the left and turning south-southeast for several miles along the border between Marple Township and Haverford Township. In this reach, the creek flows alongside Interstate 476 and crosses it once. As it continues downstream alongside the highway, it crosses Pennsylvania Route 3 and receives the tributary Longford Run from the left. Near Pilgrim Gardens, it turns southeast again and begins to flow along the border between Upper Darby Township and Springfield Township, crossing US Route 1 and receiving the tributaries Colleen Brook and Lewis Run from the left and right, respectively. Further downstream, the creek's valley becomes much steeper and narrower and it makes several meanders as it passes by Clifton Heights and Landsowne before flowing along the border between Aldan and Yeadon. The creek then flows south-southeast for a few miles, leaving its valley and passing Darby, Collingdale, Sharon Hill, and Colwyn as it crosses US Route 13. It then receives the tributary Cobbs Creek from the left. The creek turns south and enters the John Heinz National Wildlife Refuge 4.5 miles upstream from its mouth. At this point it passes through the largest freshwater marsh in Pennsylvania before becoming entirely tidal. It turns west-southwest for a few miles, passing by Philadelphia, Folcroft, Norwood, Prospect Park, Tinicum Township, and Ridley Township and receives the tributary Muckinipattis Creek from the right. Darby Creek winds through a large lagoon 30 ft deep in places that was dredged in the 1960s. The creek then receives Stony Creek, its last named tributary, from the right and turns south for a few tenths of a mile before reaching its confluence with the Delaware River. Darby Creek joins the Delaware River upriver of its mouth. Tributaries Tributaries of Darby Creek include Cobbs Creek, Little Darby Creek, Ithan Creek, Muckinipattis Creek, and numerous others. Muckinipattis Creek joins Darby Creek upstream of its mouth and its watershed has an