The three books series - “How the U.S. Government Works," " Presidential Elections," and the "U.S. Constitution,” by Syl Sobel is a great way to introduce elementary children to simple concepts concerning the United States Government.
The information is written in easy to understand large print and there are plenty of illustrations. Some of the topics that are covered include the three branches of government, taxes, law making, electoral votes, election process, checks and balances and the Bill of Rights.
What I love is that they are easy enough reads that kids can sit in your lap and enjoy them as though they were fiction. Just enough trivia and knowledge of historical people have been included to enhance this otherwise dry information.
If you are looking to introduce democracy and the basics of American Government this is a great start and children will use it as a base to grow their knowledge as they mature.
Here are two interactive websites to help with your studies: