I have heard for 35 some years or more, that American history books where revised and changed in the 1920's to what is read now buy students. My son is a major American history buff, and i would like to get him an American history book that was written before American history was changed (if it was?) Any recommendations on what title, and where to buy one? I am not looking for a collectors addition, a fairly good shape used text book would work out fine.

Hit up used book stores and look around. I see old school books all the time that cover a large variety of subjects. If you are ever in Ft Smith AR there is a really good one downtown that has them broken up in sections.

I purchased a bunch of them in less than perfect condition on eBay for 5 to 10 bucks each.  The older they are the more fragile they are.  Most of the books that I bought were pre-1900 and some as old as 1840.  Most of them are old school history books and what I found is that most if not all of these can be downloaded for free in multiple formats at archive.org.  Even though I own original books I prefer to download a scanned copy and read it on my iPad.  I will post some links for you.

Here is a good example of one from 1884.  https://archive.org/details/elementaryhistor00quac

Another from 1839 https://archive.org/details/johnfrostsushist00frosrich

What I found was much more detail and history that I had never heard of before.  A book on American History written in 1839 had to fill the pages with much less history than one written in 1939.  You will find some of the books discuss the Mound People in great detail.  Apparently there were ancient mounds all over the USA from a people that pre-date the Native American Indians.  Also, there is just so much more detail on certain subjects that some of it is boring and some of it is interesting.  
What shocked me was when I purchased a set of 1923 World Book Encyclopedia's and compared them to my set from 1977.  Talk about rewriting history.  It was insane.  I have since given away the 1977 but I still have the 1923.

For world history. Look into "The Story of Civilization" by Will and Ariel Durant. Before Revisionist history movement took hold. It's 11 Volumes.
The Story of Civilization.

That is an amazing set of books.  I own one book from the set and it is amazing.