Return a Metro City after matching a mailing city with a suburb

Hi, I'm trying to match a suburb city with its Metro area city, what I'll call the "Market City." I've got the names of the Market City as headers (I1:T1) with their suburbs listed below. I can't figure out a formula that will index/search/match the mailing city to the suburb and return the Market City. I was able to use nested IF functions for a lot of the large markets, but that doesn't take care of everything.

Is this possible or do I need a Macro? In column H, you can see the formulas I've tried; I thought a reverse lookup might be the way. There are also a few duplicates; I'm not sure how to incorporate those. I've also replaced the blank cells in the Market array (I2:T24) with spaces.

Thanks!

Maybe put this on H2 and copied down as necessary

=IFERROR(INDEX($I$1:$T$1,SUMPRODUCT(($I$2:$T$24=$D2)*COLUMN($I$2:$T$24))-COLUMN($I$2)+1),"")

That worked! Thanks so much! Now I just have to study it so I understand how it works.

Actually, before I close this thread, what's the best way to account for duplicates? If I have a Highland Park, TX and a Highland Park, IL (need to add in to the Sample file I uploaded), the formula returns blank.