Although I am not a history teacher, I am aware of a free app available through the iTunes store provided by World Book: WORLD BOOK - This Day in History for iPad on the iTunes App Store. I checked on interactive textbooks available by Pearson, McGraw Hill, and Houghton Mifflin Harcourt, and I did not find any iBook textbooks for iPad specific to U.S. History. However, other Community members may be using some provided by different publishers.
I realize this does not exactly answer your question, but hopefully these resources will give you some ideas. You also may want to join the group iPad and contact some of the members regarding their use of interactive textbooks especially for U.S. history.
Let us know how your search progresses in finding high school interactive texts. How many iPads do you have available for your students?
Is your school using interactive textbooks for iPads in any other subjects? If yes, what are they using? Do they find interactive textbooks more engaging for student learning than the hard copy texts?
Thanks Lynne. We just started piloting our first IPad equipped classroom. It is a special education US History class at the high school level. I'll try to keep the community updated with our progress. Thanks