Changing a Property's Address

[Garen Lafser]

Hello All and thank you in advance for looking at this and hopefully helping!

I have a building that I am wanting to change the address of and I can't seem to find out how to start the process.  Reason for wanting to change is that our address is currently 4398 Chouteau EF (although on the tax records it is only 4398 Chouteau, but so is another property on the street - very confusing).  We are adding 5 apartments and two commercial spaces and we don't want an apartment to be "4398 Chouteau EF unit D".  Just too long and confusing.  We are at a corner so we would like to take the other street's name.

Any ideas where to start?  Postal Service or the City?  I'm in St. Louis City and the people I have spoken to are of little to no help unfortunately.

Thanks!