Many of the parks in Maryland, along with Rock Creek Park in the District, have facilities that residents of either jurisdiction can reserve for private use.
Reserve an athletic field, pincnic area, or recreation center in a Montgomery County Park or in Rockville's Civic Center Park.
To reserve a picnic area in Rock Creek Park, it is best to go to the Department of Parks and Recreation headquarters. There is a $7 fee. Call before you go to check the availability of the site you'd like to reserve. Otherwise, you can download a form and mail it in.
DC Department of Parks and Recreation Contact Information:
Phone: (202) 673-7449
Fax: (202) 671-2852
DC Department of Parks and Recreation
3149 16th Street, NW
Washington, DC 20010