Once, it cost 3 cents to mail a letter

When you picked up your mail Monday, you may have noticed something different. Did you catch it?

Here's a hint: You'll see this change on the upper right-hand corner of any piece of first-class mail that weighs an ounce or less.

Sunday the US Postal Service increased the price of a first-class stamp from 37 cents to 39 cents.

The last price increase was in 2002, when the cost to send a letter rose by 3 cents. In 2001, a first-class stamp was 34 cents.

The US Post Office Department was created by Congress in 1775. (It was renamed the US Postal Service in 1971.)

The cost to send a letter in 1845 was about 5 cents - but that was the equivalent of about $10 today.

In 1851 Congress wanted to make the mail service more affordable. So it reduced the cost of a first-class stamp from 5 cents to 3 cents. For the next 107 years, the price remained about the same.

In 1958, the cost of a first-class stamp increased to 4 cents. Since then, the cost of stamps has risen every few years. These increases help the postal service keep up with the costs of processing and delivering the mail.

You don't have to throw out your old 37-cent stamps: The postal service has issued 2-cent stamps. This way, you can use a 2-cent stamp and an old 37-cent stamp until you get the new 39-cent stamps.