5 Numbers That Changed American History

Before the 1960s, mailing addresses included the recipient's name, house number, street, city, and state. For many people, street names were replaced with "RD 1." or another number with RD standing for "rural delivery." This changed as populations grew, and the ZIP code made mail sorting and delivery more efficient. Learn the history of the United States Postal Service's mailing system, and discover why were ZIP codes invented. (Also, find out "When – and Why – Area Codes Were Invented.")

It used to be only city dwellers qualified for mail delivery to their homes or businesses. By 1890, about 65% of Americans lived in rural areas and picked up their mail at the local post office. Americans questioned why people near cities received mail at home, while those in the country were forced to make long trips to post offices. Postmaster General John Wanamaker realized it made sense for one carrier to deliver to dozens of people rather than have everyone travel to town.

Wanamaker's "Bill to Extend the Free Delivery System of Mails" failed, however it captured attention. The new postmaster general agreed to test rural free delivery provided the government help pay. Congress provided a total of $40,000 in 1895 to test the effectiveness of mail delivery to country homes.

Three West Virginian towns were chosen for rural mail delivery. Why West Virginia? It's where Postmaster General William Wilson lived. By the end of the year, rural delivery service expanded to 29 states and proved successful.

After several years of successful mail runs, rural free delivery became a permanent service. Rural delivery officially launched on July 1, 1902. Under this new system, people received mail to their town with or without a street or an RD or RFD route number. Meanwhile, the recipient's last name, town, and state helped establish the correct mailbox.

At this point, whatever residents found suitable for holding mail was used. It might be a metal pail hanging on a fence post or a wooden crate nailed to a tree. Postal authorities provided new rules regarding mailboxes. Weatherproof boxes measuring 6 x 8 x 18 inches were manufactured. Boxes had to be attached to a post at a height convenient for the mail carrier to stay in the vehicle. Locks on the boxes had to be easily opened with "one gloved hand." Most importantly, customers had to install them by 1902 to continue receiving their mail.

In 1904, mail carriers could only deliver packages weighing up to 4 pounds. With no other option, senders arranged delivery of heavier packages through another service. To meet the growing need, the Post Office Department requested better equipment to transport heavier packages. However, it took until 1911 to gain congressional approval.

With mail and packages going straight to homes from regional sorting centers, post offices were no longer needed in certain areas. While there were almost 77,000 post offices in 1901, that number started to decline. Today, there are 31,123 post offices throughout the U.S.

WWII wreaked havoc on the number of trained postal workers available to sort and deliver mail. With employee counts down after WWII and limited resources for hiring and training new employees, Postal Inspector Henry Bentley Hahn, Sr. looked for new ways to handle the increasing amount of mail.

By 1961, the United States Postal Services (USPS) was handling about 43 million pieces of mail each week. Hahn proposed a new mailing system to C. C. Garner, the Postal Inspector. That proposal led to the "Zone Improvement Plan." That plan established five-digit numerical codes to use for sorting and delivering mail throughout the U.S. With the help of Robert Moon, Hahn established a new way to mail items using a new ZIP code system.

The "Zone Improvement Plan" – ZIP for short – established a three-digit code starting with one of 10 service areas ranging from 0 to 9. Moon created the service areas and Hahn developed how the fourth and fifth digits would work. The public started using a ZIP code on July 1, 1963.

The first three digits of a ZIP code include the number for the service area and the city or distribution area.

• 0 – New England, New Jersey, Puerto Rico, Virgin Islands, and APOs and FPOs in Europe
• 1 – Delaware, New York, and Pennsylvania
• 2 – Maryland, North Carolina, South Carolina, Virginia, Washington D.C., and West Virginia
• 3 – Alabama, Florida, Georgia, Mississippi, Tennessee, and APOs and FPOs in the Americas
• 4 – Indiana, Kentucky, Michigan, and Ohio
• 5 – Iowa, Minnesota, Montana, North Dakota, South Dakota, and Wisconsin
• 6 – Illinois, Kansas, Missouri, and Nebraska
• 7 – Arkansas, Louisiana, Oklahoma, and Texas
• 8 – Arizona, Colorado, Idaho, New Mexico, Nevada, Utah, and Wyoming
• 9 – Alaska, California, Guam, Hawaii, Oregon, Washington, APOs and FPOs in the Pacific, and U.S. territories in the Pacific

The fourth and fifth digits cover which post office gets the piece of mail. Take the TV show "Beverly Hills 90210" and learn the structure of that famous ZIP code. The first three digits "902" cover California and Los Angeles, and "10" is the Beverly Hills area.

As the population grew, four additional digits joined to the structure of a ZIP code in 1983. These new numbers joined the old ZIP code with a dash separating them. The additional four digits detail the block and section or side of the street the address is on. Use your address to find your four-digit code from the USPS.

The E-911 system is relatively new to the U.S. In 1991, authorities implemented E-911. Rural homeowners needed to post their 911 house number on their mailbox and house. This enables first responders to quickly find a house. House numbers are based on the number of yards from the driveway to a cross street. The USPS updated rural mailing addresses to match the 911 address, except for people with P.O. boxes.

Suppose your grandparents live 120 yards down Maple Street in the 1940s. Their USPS address looked like this:

• First and last name
• RFD 4
• City and State

Today, it looks like this:

• First and last name
• 120 Maple Street
• City, State, and ZIP+4

Speaking of old addresses, many older adults have old letters and postcards tucked away in storage. Some antique postcards and envelopes sell for hundreds of dollars. Discover other items hiding in your grandparent's basement or attic that are worth a lot of money.