Spurred by concerns about growth and traffic congestion in Southern Maryland, Charles County and neighboring Prince George’s County have partnered to launch a bus line that provides, for the first time, a mass transit connection between the jurisdictions.

In an area long underserved by public transit, the new line will help connect people to Metro and other regional transportation systems.

“We have been screaming for this for years and finally it happens,” said George Clark, a ride-share coordinator with the Tri-County Council for Southern Maryland. Clark gets about 40 calls each month from Charles residents inquiring about transit options to get to Prince George’s, the District or a Metro station.

The new route was launched by the Prince George’s transit system, which is known as TheBus. The No. 36 began running July 1, serves communities south of Clinton and crosses into Charles.

The line offers an alternative for people commuting to jobs at popular commercial centers such as Brandywine Crossing in Prince George’s and Pinefield South Shopping Center in Waldorf. In Clinton, riders also are able to transfer from the No. 36 to other buses that connect to the Metrorail system.

For Charles residents, it is an important link, said Clark, even if it takes them hours to get to their destination through multiple transfers and in buses that don’t run as often as in the District.

“It might take them half a day, but they will be able to get to the Metro station from the northern part of Southern Maryland,” said Clark. “Now they can get across the county line, and that’s all everybody wanted.”

Ridership was light the first couple of weeks, but residents, bus drivers and community leaders predict ridership will grow as word of the route spreads.

The transit systems in both counties have grown more popular in the past five years. Ridership of TheBus jumped to 4.5 million in 2012 from 2.8 million in 2007. VanGO, the transit system in Charles, has seen a 60 percent ridership increase since 2007.

The three commuter buses that the Maryland Transit Administration runs from Charles to the District have reached capacity, state officials said. Those buses are northbound in the mornings and southbound in the afternoons, and are often standing room only. The park-and-ride lots are increasingly overcrowded, officials said.

The MTA plans to expand to five routes in October, pending approval by the Board of Public Works.

Those buses, however, are not convenient for many local commuters because they are express rides into the District and unavailable for midday travel.

Officials and community leaders say the heavy use of those buses indicates the need for more transit options from Southern Maryland.

In Charles, the demand for transit has increased as many residents have taken entry-level and service jobs in Prince George’s.

One of Maryland’s fastest growing counties, Charles saw its population rise by about 22 percent from 2000 to 2010. The expansion was fueled by the arrival of minorities, mostly blacks, Hispanics and Asians, many of whom came from Prince George’s.

“We have gone from being a mostly rural county to being a bedroom community of Washington,” said Charles County Commissioner Ken Robinson. “The result of that is we have a lot of commuters, and a lot of those commuters work in Prince George’s as well as in Washington, D.C.”

Charles and Prince George’s officials say they expect more collaboration on transportation and traffic concerns. A rapid transit bus system and a light-rail system have been discussed, but in the near term, an expansion of traditional bus service is the most likely option.

The new bus service is part of a $3 million investment the Prince George’s transit system is implementing this summer to expand bus service into southern parts of the county. As part of the investment, TheBus is also planning to expand the No. 35 route, which currently offers only four trips a day to the booming National Harbor development.

Before the No. 36, points south of Clinton in Prince George’s had not been served by any fixed bus routes.

In recent years, construction has picked up at Brandywine Crossing, now a shopping destination for residents from southern Prince George’s as well as Charles. Home to Target, Costco and Marshalls, the shopping center opened a movie theater three months ago. Restaurants and a Carmax are on the way.

“This area needs this bus. It needs transportation, period,” Clinton resident Carlton Ford said. Ford, 62, drives daily to work at the Brandywine Crossing Target, but with no transit option he had a hard time when his car failed him.

Richard Lintker, general manager at the new Xscape Theatres, said he sees the bus becoming an important connection for the center, which has seen good business and continues to grow. Theater employees, about one-third of whom don’t have their own transportation, would benefit from the bus line, Lintker said.

On a recent day, the No. 36, with just one rider, traversed parts of southern Prince George’s that maintain a rural feel, with farms and country roads. It reached commercial areas every 40 minutes. Some residents at the Clinton Park and Ride, the first stop, asked the driver where she was headed. Some were surprised to see “Waldorf” on the display system.