Usually, very large, slow loading maps will be in the .jpg format, which is a very compressed format just for such files. It makes no sense converting such files to .gif since they would be many times larger. You just have to get your hands on some software to handle both kinds. The maps that work best for what we will be doing are usually not highly detailed. Often, a county will show only the county name and be distinguished from other counties by a different color.
County lines are important in genealogy but are often very difficult to see in a conventional atlas.
One thing that I did not do as I went along that I should have done was to record where I found each map. It really is a good idea to do that. Let me put a little special emphasis on the word personal . What you will be making is copy 1 of 1. It is intended for your own personal use and not readily reproducible.