Be sure to check your county and city ordinances. In the area I live in (edge of the Washington DC metro area in northern Virginia) it is illegal to discharge any projectile weapon (including an air gun) within an urban area.
New law in Virginia (2011)...
Summary
“Pneumatic gun regulations. Prohibits a locality from adopting an ordinance that prohibits the shooting of pneumatic guns on private property, with permission of the owner of the property, if reasonable care is taken to prevent a projectile from crossing the bounds of the property. The bill also invalidates any existing local ordinances that conflict with the provisions of the act.”
From the 2011 session - SB 757 Pneumatic guns; regulations, exceptions.
http://lis.virginia.gov/cgi-bin/legp604.exe?111+sum+SB757
New state airgun law worries Fairfax(VA)
http://www.freerepublic.com/focus/f-news/2730511/post
Yes, indeeed, we must still check the local ordinances, as the new law contains this...
"A. A locality may prohibit, by ordinance, the shooting of pneumatic guns in any areas of the locality that are in the opinion of the governing body so heavily populated as to make such conduct dangerous to the inhabitants thereof..."