The USPS is legally obligated to serve all Americans, regardless of geography, at uniform price and quality.

Article I, Section 8, Clause 7 of the United States Constitution, known as the Postal Clause or the Postal Power, empowers Congress "To establish Post Offices and post Roads"

According to USPS documents, as of 2011, the USPS operates 31,000 post offices and locations in the U.S., and delivers 177 billion pieces of mail annually.

First-Class mail volume (which is protected by legal monopoly) peaked in 2001 and has declined 29% from 1998 to 2008. Lower volume means lower revenues to support the fixed commitment to deliver to every address once a day, six days a week. In response, the USPS has increased productivity each year from 2000 to 2007, through increased automation, route re-optimization, and facility consolidation.

But the USPS has its hands tied...

"...restructuring the $5.5 billion annual Retirement Health Benefit (RHB) prefunding requirement, imposed by Congress in 2006, would save far more money (than closing branches) without any negative impact on mail service or the solvency of USPS pensions. That 2006 law required that the USPS prefund 100% of anticipated retirement and retirement health costs, a requirement that no other public or private entity in America faces. By comparison, many AAA rated localities and states prefund retirement up to 80%."

-Congressman Gerry Connolly (VA) & Don Young (AK)