Apples and orchards

20th century[edit]

The advent of Rural Free Delivery (RFD) in the U.S. in 1896, and the inauguration of a domestic parcel post service by Postmaster General Frank H. Hitchcock in 1913, greatly increased the volume of mail shipped nationwide, and motivated the development of more efficient postal transportation systems.^[29] Many rural customers took advantage of inexpensive Parcel Post rates to order goods and products from businesses located hundreds of miles away in distant cities for delivery by mail.^[30] From the 1910s to the 1960s, many college students and others used parcel post to mail home dirty laundry, as doing so was less expensive than washing the clothes themselves.^[31]

After four-year-old Charlotte May Pierstorff was mailed from her parents to her grandparents in Idaho in 1914, mailing of people was prohibited.^[30] In 1917, the Post Office imposed a maximum daily mailable limit of two hundred pounds per customer per day after a business entrepreneur, W. H. Coltharp, used inexpensive parcel-post rates to ship more than eighty thousand masonry bricks some four hundred seven miles via horse-drawn wagon and train for the construction of a bank building in Vernal, Utah.^[32][33]

The advent of parcel post also led to the growth of mail order businesses that substantially increased rural access to modern goods over what was typically stocked in local general stores.

Historic Mineral Wells, Texas post office built between 1911 and 1913

In 1912, carrier service was announced for establishment in towns of second and third class with $100,000 appropriated by Congress.^[34] From January 1, 1911, until July 1, 1967, the United States Post Office Department operated the United States Postal Savings System. An Act of Congress of June 25, 1910, established the Postal Savings System in designated Post Offices, effective January 1, 1911. The legislation aimed to get money out of hiding, attract the savings of immigrants accustomed to the postal savings system in their native countries, provide safe depositories for people who had lost confidence in banks, and furnish more convenient depositories for working people. The law establishing the system directed the Post Office Department to redeposit most of the money in the system in local banks, where it earned 2.5 percent interest.

The system paid 2% interest per year on deposits. The half-percent difference in interest was intended to pay for the operation of the system. Certificates were issued to depositors as proof of their deposit. Depositors in the system were initially limited to hold a balance of $500, but this was raised to $1,000 in 1916 and to $2,500 in 1918. The initial minimum deposit was $1. In order to save smaller amounts for deposit, customers could purchase a 10-cent postal savings card and 10-cent postal savings stamps to fill it. The card could be used to open or add to an account when its value, together with any attached stamps, amounted to one or more dollars, or it could be redeemed for cash. At its peak in 1947, the system held almost $3.4 billion in deposits, with more than four million depositors using 8,141 postal units.^[35]

The Post Office Department played an important intelligence role during World War I, implementing the Espionage and Trading with the Enemy Acts, monitoring foreign mail and acting as counter-espionage to help secure allied victory.^[36]

On August 12, 1918, the Post Office Department took over airmail service from the United States Army Air Service (USAAS). Assistant Postmaster General, Otto Praeger, appointed Benjamin B. Lipsner to head the civilian-operated Air Mail Service. One of Lipsner's first acts was to hire four pilots, each with at least 1,000 hours' flying experience, paying them an average of $4,000 per year ($65.1 thousand today). The Post Office Department used new Standard JR-1B biplanes specially modified to carry the mail while the war was still in progress, but following the war operated mostly World War I surplus military de Havilland DH-4 aircraft.^[37]

During 1918, the Post Office hired an additional 36 pilots. In its first year of operation, the Post Office completed 1,208 airmail flights with 90 forced landings. Of those, 53 were due to weather and 37 to engine failure. By 1920, the Air Mail service had delivered 49 million letters.^[37] Domestic air mail became obsolete in 1975, and international air mail in 1995, when the USPS began transporting First-Class mail by air on a routine basis.

The Post Office was one of the first government departments to regulate obscene materials on a national basis. When the U.S. Congress passed the Comstock laws of 1873, it became illegal to send through the U.S. mail any material considered obscene or indecent, or which promoted abortion issues, birth control, or alcohol consumption.^[38]

On March 18, 1970, postal workers in New York City—upset over low wages and poor working conditions, and emboldened by the Civil Rights movement—organized a strike against the United States government. The strike initially involved postal workers in only New York City, but it eventually gained support of over 210,000 United States Post Office Department workers across the nation. While the strike ended without any concessions from the Federal government, it did ultimately allow for postal worker unions and the government to negotiate a contract which gave the unions most of what they wanted, as well as the signing of the Postal Reorganization Act by President Richard Nixon on August 12, 1970. The Act replaced the cabinet-level Post Office Department with a new federal agency, the United States Postal Service, and took effect on July 1, 1971.