Википедиа:Online maps of the United States

Maps of the United States are available in various media.

On Wikipedia and Wikimedia Commons

Several useful "starter" maps for modification:

Image:Blank US Map with borders.svg, a blank states maps with borders.
Image:BlankMap-USA.png, a map with no borders and states separated by transparency.
Image:USA labelled map.svg, a map with two-letter state abbreviations.
Image:US map - geographic.png, a geographical map.

On Wikimedia Commons, a free online media resource:

commons:Category:Maps of the United States, the category for all maps with subcategories.

On Wikipedia itself:

Category:Maps of the United States for maps of all varieties by subcategory.
- Category:United States maps for maps of the entire United States.
Category:Geography of the United States, for general articles on the topic.

Perry-Castañeda Library Map Collection - United States has an extensive online collection of scanned historical maps of the US, and a list of other map sites.
Charting North America, maps and atlases in the New York Public Library Digital Collection
Online digitized versions of many 18th- and 19th-century American atlases, as well as the 1897 Rand McNally Indexed Atlas of the World and many other maps, can be found at DavidRumsey.com.
Hipkiss' Scanned Old Maps from Atlases and any old books with maps in them!