MD 190 begins at a three-way intersection just east of the hamlet of Seneca near the mouth of Seneca Creek at the Potomac River. The east leg of the intersection is MD 112 (Seneca Road), which heads toward Darnestown. The west leg of the intersection is county-maintained River Road, which parallels the river through the Seneca Historic District and peters out beyond McKee-Beshers Wildlife Management Area south of Poolesville. MD 190 heads southeast as a two-lane undivided road that parallels the Potomac River from a distance. The road intersects several county highways that provide access to the Chesapeake and Ohio Canal National Historical Park. The highway crosses Muddy Branch within Blockhouse Point Park and continues through the Travilah area, where the highway intersects Travilah Road. MD 190 crosses Watts Branch west of Piney Meetinghouse Road, where the Potomac River curves south away from the highway. The route crosses Rock Run as it enters the village of Potomac, where the highway temporarily expands to four lanes and intersects Falls Road, which heads north as MD 189 and south toward Great Falls. MD 190 passes to the north of the TPC Potomac at Avenel Farm golf course and intersects Bradley Boulevard, which carries MD 191 north of MD 190, west of the entrance to Congressional Country Club.