Happy Flag Day! In the U.S., June 14 is an officially designated day that celebrates the anniversary of the adoption of the Stars and Stripes as the official U.S. flag in 1777. 

In the U.S., each state has its own particular flag, bursting with symbolism and pride. For example, the striking and colorful flag of Maryland features the 17th Century coat of arms of the family of Sir George Calvert, the first lord of Baltimore. And Indiana's flag features 18 small gold stars and one additional larger star, representing Indiana's admission to the Union as the 19th state.

So to celebrate this flag-tastic day, here are our top ten facts about the official U.S. state flags. And, after reading this, if you think you're up to a flag-tastic brainteaser, take our State Flag Quiz!

1. Only four state flags do not include the color blue. They are the flags of: Alabama, California, Maryland, and New Mexico.

2. Oregon is the only state that has a two-sided flag, featuring the state seal on the front side and the state's official animal — the beaver — on the backside. Massachusetts had a two-sided flag up until 1971 when a single-sided version was adopted.

3. Washington state has two unique features: First, it's the only flag that features a green background. Second, it is the only flag with the likeness of an American president (George Washington).

4. Ohio is the only state flag that is not some form of rectangle, as the outer edge features a forked tail. 

5. The upper left-hand corner, or "canton," of Hawaii's flag features the British flag — a remnant of the British involvement in the islands.

6. There are about 15 state flags with blue backgrounds featuring some form of state seal or imagery on the front, making them a bit more difficult to distinguish from one another.

7. Animals are popular for state flags, specifically the California bear, Oregon beaver, Wyoming bison, and Louisiana pelican.

8. To this day, there is a debate about whether the crescent in the upper-left corner of the South Carolinian flag is a moon or a "gorget," a silver crescent worn on the front of the caps of the South Carolina troops during the American Revolutionary War.

9. Oklahoma's flag represents the melding of cultures. The flag shows a traditional buffalo-skin shield of the native Osage Nation, with seven eagle feathers on a blue background inspired by the flag of the Choctow. On top of the shield, crossed, is a ceremonial pipe representing the Native Americans of the Plains, and an olive branch to represent European Americans.

10. New Mexico's striking flag features the sun symbol of the indigenous Zia people.

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