North of Bethlehem, the Monocacy Creek is a spring-fed, limestone creek known for its wild brown trout. The headwaters of Monocacy Creek are above the town of Bath and it runs downstream to the Lehigh River confluence near Bethlehem.
North of Bath, there is a nice, shady 1.9 mile Wild Trout Water section from SR987 bridge downstream to SR248 bridge. Fly fishing access for this upper section of Monocacy Creek is off SR512.
South of Bath, there is a good fly fishing section of the Monocacy that is stocked starting at the SR512 bridge running downstream to the US22 bridge.
Just before entering Bethlehem, there is a another good section below US22. There is a 1.9 mile Class A Trout Water section from Gertrude Fox Conservation Area downstream to Illicks Mill Dam. There are wild brown trout since stocking is prohibited here.
Overall, Monocacy Creek is the 16th most popular fly fishing river of all 49 fly fishing spots in Pennsylvania.