Biden was declared the winner of Tuesday’s primary on a night when six other states and the District of Columbia are voting in the presidential nomination contest. The result has been expected because Biden’s rivals have already dropped out of the race.
President Donald Trump won the Republican presidential primary in Maryland.
Voters in Maryland were strongly urged to vote by mail because of concerns about further spread of the coronavirus.
Biden’s haul of delegates from his Maryland win and victories in Pennsylvania, Rhode Island and Indianan push him closer to the 1,911 delegates he needs to capture the Democratic presidential nomination.