WAKE COUNTY — It claims to be the No. 1 small town in North Carolina, but the town of Apex is growing without even adding a single resident. The town has outgrown its zip codes.

Sue Williams thought she was moving back home to Cary, but imagine her surprise when she found out she is living in Apex.

"One company had us listed as a Raleigh address, one had a Cary address," Williams says. "The major problem has been confusion, the fact that we live in Cary, but have an Apex address."

It all boils down to ten numbers, 27511 and 27513. They are Cary's current zip codes, but thanks to the explosive growth, the U.S. Postal Service has run out of room.

"It's gotten to a critical point in the past few years," says Chris Tinkham, Cary Postmaster. "It's like the 1-800 numbers, the sector within a zip code can only hold so much."

The situation has left more than 10,000 Cary residents living with Raleigh, Durham, Morrisville and Apex addresses.

"It's more of a pride thing," Williams says. "When I say I live in Cary, I want to be able to write Cary, N.C. on my address."

The confusion has caused delays in deliveries, but homeowners worry the mailbox mess may create more serious problems.

Apex firefighters agree. They say a correct address is critical information.

"Their 911 calls go to Cary, and then they say an Apex address," says Apex firefighter Chad Edmunds. "It's confusing whose district it is, so dispatchers have to discuss between each other whose district it is."

The zip code problem has been growing for a couple of years, but the post office says it is looking for a solution. Cary may receive a new zip code, 27518.