Produce the block maps. The FORMAT statement assigns SITESFMT. to the response variable. DISCRETE specifies that each formatted value is a separate response level. AREA= specifies that the map surface should be patterned by the first variable in the ID statement, REGION. CBLKOUT= and COUTLINE= specify the color that outlines the blocks and the regions, respectively. 
proc gmap map=reflib.states2 data=reflib.sites;
   format sites sitesfmt.;
   id region state;
   block sites / discrete
                 area=1
                 legend=legend1
                 shape=block
                 cblkout=black
                 coutline=black;
run;
quit;