Route 124 begins at the intersection of US 202 and CR 510 at the Park Place square in the downtown of Morristown, Morris County.

[1] A short distance later, CR 601 continues southeast on South Street and Route 124 bears left to head east on Madison Avenue, coming to an interchange with Interstate 287.

Past this interchange, the road passes Morristown Memorial Hospital and continues through mainly commercial areas with some homes.

At the intersection with Normandy Parkway, the route turns to the southeast and enters Morris Township, where it narrows to two lanes again, with NJ Transit’s Morristown Line running a short distance to the northeast of the route near the Morris County Golf Club.

Past this intersection, the road passes between residential neighborhoods to the northeast and Drew University to the southwest.

Route 124 crosses over the Morristown Line near James Park and becomes Main Street, heading southeast through the commercial downtown of Madison.

[1] Past the Rosedale Avenue intersection, the route heads into a mix of residential and business areas.

The road passes to the south of The Mall at Short Hills before running through the Canoe Brook Country Club.

[1] In 2013, City of Summit vacated the 50-foot public right of way of the old road section from Route 124 into the current Brantwood Drive.

At this intersection, Route 124 entirely enters Springfield Township and becomes Morris Avenue, passing a mix of residences and businesses.

[1][2] The two directions of Route 124 rejoin and follow four-lane divided Springfield Avenue northeast to a crossing of the Rahway River and a partial interchange with I-78.

At this point, Route 124 crosses into Maplewood, Essex County and becomes a three-lane road with a center left-turn lane that is locally maintained.