There are quite a few around my area (Hunterdon County, NJ), nice old ones, but they're mostly inaccessable, usually in areas where you can't park nearby. But they're kept reasonably clean, something that doesn't often happen when cemeteries get old.

My favorite visitable one is Woodlawn in the Bronx. Duke Ellington is buried there, along with a number of really grand mauseleums of well-known American families. They're worth checking out for the over-done architecture.