Downloading geographic boundary shapefiles from the U.S. Census Bureau is straightforward. Here's how to do it for any location in the United States. This is also a simple way to get "study area" shapefiles for Risk Terrain Modeling (RTM).
1. Open American FactFinder (http://factfinder.census.gov)
2. Click on "Advanced Search" (menu options at the top of the screen)
3. Search for a geography in the "state, county, or place" text box (E.g. Newark city, New Jersey)
4. Click on "Geographies" tab on the left side of the webpage, then click on the "Maps" tab