There are two maps in the film.  One is important to the plot, the other not at all. The first is given to Slaughter by a police officer who wants him to burgle a gangster's safe.

The map is then shown by Slaughter to the former safe-cracker (now pimp) with whom he will carry out the burglary:

The details of the map are either too feint or too distant to be readable, but it is anyway the idea of the map that counts for the story.

The other map is readable, and is presumably of Los Angeles (where the film is set and shot), but it serves only as establishing décor in an office where the gangster's takings (from prostitution, gambling etc.) are being added up:

This map can be seen in the background when Slaughter launches his one-man revenge attack at the climax of the film: