Route J4 operated between Bethesda and Beltway Plaza Mall until 1978 when it was shorten to operate between Silver Spring station and Bethesda being replaced by route F6. Around the 1980s, route J4 was extended to Montgomery Mall to serve alongside the Bethesda-Silver Spring Line with routes the J1, J2, and J6. However the route was discontinued in the 1990s.
Planning
In the late 1990s to early 2000s, the Maryland Department of Transportation had a goal of providing service between College Park and Bethesda. Maryland already implement the C8 between Glenmont and College Park and later extended to White Flint in 2000. The Purple Line was mentioned during the 1990s but with high construction costs and delays led the project to be in the talks until construction began in 2017. Originally, the plan between College Park and Bethesda was to have an Bus rapid transit opposed to a light rail.
New Route J4
While the purple line was still in talks, WMATA and the MTA created route J4 to operate between College Park station and Bethesda station on April 15, 2002. Route J4 was created in order to meet the Maryland Department of Transportation's goal of providing better transportation between the University of Maryland and various places throughout Montgomery County, Maryland. Route J4 was also created by WMATA to provide limited stop service between the College Park–University of Maryland station and Bethesda station via the University of Maryland, Langley Park, and the Silver Spring station, which the Maryland Department of Transportation originally had as a goal for its Purple Line light rail trains to operate on. However, since the Purple Line was yet to be built and had a long way to go in terms of getting the necessary funding and approval from Prince George's County, and Montgomery County. The J4 provides extra service for the J1 and J2 along East West Highway and C2, C4 along University Boulevard. The J4 becomes a local route between University Of Maryland and College Park station serving all stops. The J4 became a MetroExtra route since 2007, as part to increase more service from Routes J1 and J3. This brings faster service on the J4, as the MetroExtra conversion is part of a collaboration between the MTA and WMATA.
2015 Service Changes
With the Silver Spring Transit Center's opening in 2015, J4 going Eastbound was given Bus Bay 223 on Level 2 along with the F4, while J4 going Westbound was given Bus Bay 102 on Level 1 along with routes J1 & J2.
September 2019 changes
Beginning on September 1, 2019 for nine months, the College Park Metrobus loop was temporarily closed for construction of the Purple line at College Park station having all stops located along River Road. As of a result, route J4 was temporarily rerouted along River Road having to turn around on the roundabout along Haig Drive to return to its regular route going to Bethesda.
Beginning on April 20, 2020, parts of Calvert Road was closed due to the ongoing construction of the Purple line, route J4 was temporarily rerouted along US Route 1 and to turn on Calvert Road to serve the west side of College Park–University of Maryland station since vehicles cannot travel along parts of Calvert Road. However the reroute has not operated due to the 2019-20 COVID-19 outbreak and Metro's reduced service since March 13.
