Here's an alternative approach that's available now ...
Rather than using dummy points (which you would have to manually determine), and plotting them as invisible scatter markers, you can plot an empty choropleth polygon for the state outline. It's easier to code, and I think the state border adds value to the map 🙂
data nevada_cities; set mapsgfk.uscity (where=(statecode='NV')); run;
data nevada_border; set mapsgfk.us_states (where=(statecode='NV')); run;
proc sgmap plotdata=nevada_cities mapdata=nevada_border noautolegend; openstreetmap; scatter x=long y=lat / group=pop_type; choromap / mapid=statecode; run;
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