How To Download and Install
Downloads start automatically when you click on the file link in the tables. These are big files (up to 400 mb)! Even with a high speed connection, they can take hours.
Installation:

1. In Oziexplorer each "map" consists of 2 files--the image (many file graphic file types work), which most people would think of as the map, and the calibration file (extension .map). The images are 0.5 to 50 mb, typically about 5-15 mb.
2. The .map files contain all the necessary descriptive information--header, map name (can be independent of the USGS or other original name), image path, datum, projection, calibration points, and map boundary points. See top portion of the file in notepad below. See the map path in the third line--note there is no drive specification.
3. The .map files can be in any directory. This allows you to group related "maps" together in one location for easy navigation between files. However, the images must be in the directory pointed to by the path in line 3 above! This 'path' is the essential information that allows OziExplorer to find the image and display it. The only exception is if the .map file and image are in the same directory--Ozi looks there first, regardless of what the path says. The paths in the .map files on this site conform to the directory structure shown at the right. A 'maps' directory must start at the root of your target drive. The files are in the directories you can see under each named state, except for the the Quads, which are in subdirectories named as shown under the Arizona example. Note that the 100K and 250K maps are in the 30x60 and 1x2 directories, respectively. It was a poor decision, but after building 16,000 .map files, it's not going to change any time soon.
4. The Zipped archives may or may not have the full path information included. When unzipped, you may find that a new 'map-named state-subdirectory-sbudirectory' structure shows up. In this event, you can move the subdirectory with the files to its proper location and delete the new [and now empty] directory structure.
5. See other examples of .map files below. It should give you a good idea of how the path looks to the various directories. One point of confusion is that the directory that contains the state highway maps and other state-scale maps under each state is named simply "state." When you're navigating through the maps, you'll often wonder what state you're in until you move up one level, where the actual state name appears. Line 2 is the map name that appears in the header on Ozi. In the second and third examples below, you can see that 'Tucson' is what would be displayed for both maps, despite the fact that they are different scale maps. I've found that including a scale and even a coordinate in the 'name' helps tremendously when you need to have a clue to the adjacent maps.