Industrialization: Railway & Steamship
Postal system has its political importance, which is why it’s included in the constitution. As the US expanded, how information / news / mails were transmitted were directly influencing the limit of a united society.
The Railway mail service began as early as November 1832. In 1835, railroads accounted for only one percent of mail transportation and connected only two major cities – Washington and Baltimore.
On July 7, 1838, Congress declared all railroads to be post roads and enabled the railways to make contracts as long as sending mail by rail cost no more than 25 percent above transporting it by stagecoach.
But it’s the industrialization that enabled the US to include / connect California and other lands that are far away from the initial states.
In 1848, US acquired California at the end of the Mexican War. Under the Treaty of Guadalupe Hidalgo, Mexico also recognized the U.S. annexation of Texas, and agreed to sell California and the rest of its territory north of the Rio Grande for $15 million plus the assumption of certain damages claims.
In November 1848, Postmaster General Cave Johnson dispatched a special agent to California to establish Post Offices. By Christmas, steamships were carrying mail from New York to California via the Isthmus of Panama. This was before the construction of the canal. When the ships reached Panama, the mail was taken off and transported in canoes or on pack animals – and later by railroad – about 50 miles to the Pacific coast. Another steamship collected the mail on the Pacific side and headed north.
Congress authorized funding for the overland routes not because they brought any financial profit to the Post Office Department or the federal government, but because they helped build and bind together a nation.
Also briefly mentioned in 一朝风雨一代王：Sears, Walmart, Amazon, the expansion of the US rail transportation contributed to the growth of USPS (Post Office Department at the time).
In 1862, mail was sorted en route, as a train moved between two points, using converted baggage cars.
On August 28, 1864, the first U.S. Railway Post Office (RPO) route was established officially.
By the early 1900s, railroads were critical to postal operations. Like Union Station in Washington, D.C., located adjacent to the City Post Office Building, the Post Office Department ordered that all new main post offices in large cities be built as near as possible to the principal railroad station.