The main purpose of this legislation is to require the United States Postal Service to set up a new post office in Mountain House, California. The objective is to improve postal services for the residents of this community, which may currently lack adequate access to postal facilities. The key provision of this legislation is a directive for the Postal Service to establish the post office within one year of the law being enacted. This sets a clear timeline for when the new facility should be operational, ensuring that residents can expect improved postal services in a timely manner.