HYATTSVILLE, Md. — Sarah Leonard, 15, joined a group of local teenagers here recently as they lobbied the City Council to grant them more power. Wearing a black “I am Hyattsville” T-shirt, she stood in front of a standing-room-only crowd, sounding confident as she addressed the lawmakers.

“Hyattsville should lower the voting age to 16 so that more young people can get started being active in their communities, which will continue with them their entire lives,” Ms. Leonard said in her public remarks. “When the number of voters increases, then the city government is bound to be better represented and backed up by more support.”

Ms. Leonard appeared at a spirited public hearing here Monday night — with nearly 100 residents packing the City Council chambers and more overflowing into the hallway — to push for the ability to vote in municipal contests at 16, and take a more active role in civic life.

Ms. Leonard got her wish. After the hearing, the Council voted 7 to 4 to allow those 16 and 17 years old to vote in the town’s elections in May. Hyattsville joined Takoma Park, another Washington suburb that lowered the voting age in 2013.