The mask requirement, effective Sunday, comes as cases climb in the county and nationwide.
The update in status comes as COVID cases rise in the county.
Community members are no longer required to wear a mask for outdoor exercise.
Hogan also lifted restrictions on outdoor dining beginning Saturday.
Maryland counties had already announced similar orders requiring face-coverings.
The directive comes after Montgomery County and Washington, D.C. officials made similar orders this week.
“Just be kind to each other and check your assumptions at the door,” one student said.