There are lots of tools out there that can do hillshading on available DEMs. QGIS is one option. A reasonable dataset for maps of the US is ETOPO2.

I'm partial to Wilbur ( http://www.fracterra.com/software.html - yes, it's "not secure" because the link isn't encrypted which means that third parties can listen in on all of the secrets that the static HTML pages there will never ask you ). ETOPO2 is 10800x5400 for a world map, which might be good enough. You have to decide if you want to keep ice caps or go with the base rocks: be warned that the greenland and antarctic caps are both well over 2500'.

Here's an example from Wilbur of the ETOPO2 ice surface with the water level set to 762 meters (2500 feet). I was aiming for bluish to light blue for the current coastlines, but I missed a bit.
Click image for larger version. 

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