55802 isn't labeled in the map that Tim linked to, but it's the green splotch that covers downtown and Park Point. If you need to know a specific zip code, you can ask and I'll tell you what it is.

Okay, I can't really find an answer for why there is no 55809 or 55813. I've done a little research, however, and can now make a more educated guess. 

Before there were ZIP codes, cities had zones. ZIP stands for Zone Improvement Plan, and it added three additional digits to the zone to indicate which facility the mail is sorted at. (This, Codie, is why Duluth has a "monopoly" on 558. It's also somewhat dated as for many years now Duluth's facility sorts 556, 557, and 558. If the USPS gets its way, all of this will eventually be sorted in St. Paul.)  So while there were a lot of Zone 7s in the country, after the Zone Improvement Plan took effect, there was only one 55807.

My guess is that while there is no 55809 or 55813, there might have been zones 9 and 13 back in the 40s or 50s, which were discontinued for some reason. I have no evidence for this. It's just a guess.

Maybe if someone older than me remembers using zones while addressing envelopes, they might remember whether or not there was a zone 9 and/or 13 at some point. 

I'll end with a fun fact: ZIP codes actually have 11 digits. Each number narrows the location down a little bit further. After the five-digit ZIP comes the ZIP+4, which narrows it down to your block. At the end there's a two digit code which narrows it down to your actual house. These last two digits are not used by regular customers, but they are part of some barcoding systems.

Humans don't read barcodes, Brian.