Traci
The Center ST. or AVE. your looking for I believe is the one in Scott Twp PA. 1920 Census District 785. It's located 100 yds from the Carnegie PA border line.Only problem is the first sheet in the census is not named. Appears Carothers ST. is the first street in the census and they never did Center Street which loops around by the tracks. Compare a home owner to one that may have been there in the 1910 Census.
If you "Google Maps" Center ST it called out in Scott and Carnegie. Scott Twp zoning map will show it location ( in the orange area ) I realize Carnegie does have a Center St almost in line with the one in Scott, but kind of far away. Who knows.You already have this info from others.
You said his draft registration says Carnegie, but that may be the post office he wanted to use. I know at least for WW2 some men registered for the draft in a higher density district to try and lower their odds of getting drafted.
I did this kind of quickly, so check it out a little closer.
Will