County FIPS: 30111 - Yellowstone County, MT
This is the County FIPS:30111 Yellowstone County ZIP Code page list. Yellowstone County is a county in Montana, United States. Its detail is as below.
FIPS 30111 is not the zip code of this county, but a five-digit Federal Information Processing Standard code which uniquely identifies counties and county equivalents. You can find the zip code of cities within this county below.
Country:U.S. - United States
State:MT - Montana
And actually county doesn't have the zip code, but the city within it does, so you have to make sure what city you want to look for, then you can move on to the next step and get the corresponding zip code.
ZIP Code 5
This is an example of U.S envelope. Fill in the sender's information at the top left and the recipient information at the bottom right. The necessary information is sender/recipient's full name, street address, city, state and zip code. The recipient address information has been given for your reference. Generally, If you are not sure of the full 9-digit zip code, you can only fill in the 5-digit zip code to avoid loss of package.
For more explanation, please read the official document: USA.pdf (English)