The main purpose of this legislation is to require the United States Postal Service to create a single, unique ZIP Code specifically for Highland City, Utah. This aims to simplify mail delivery and enhance the identification of the city within postal services. The key provision of the legislation mandates that the Postal Service must designate this unique ZIP Code within 270 days of the law being enacted. This means that once the law is passed, the Postal Service has a set timeframe to implement the change.