Suburban Maryland is an important stop for anyone looking to get a full picture of the history of the nation's capital. Its two counties fuse the region's Civil War history and agricultural past with the diversity of a modern metropolis.

Montgomery County. The large swath of land across the northwest border of D.C. is Maryland's Montgomery County. Bethesda and Silver Spring, two of D.C.'s most popular suburban cities, are in Montgomery County. There's also plenty for those who love the outdoors, including Glen Echo Park and the C&O Canal National Historical Park.

Prince George's County. East of Montgomery County, also bordering the District, is Prince George's County, best known for being home to the University of Maryland Terrapins. But the county also holds an important place in America's aviation history, as it boasts the nation's oldest continuously operating airfield. Fort Washington Park provides a shady relief from the urban sprawl.