The United States flag has 13 stripes, a symbol featured in America250 commemorations. The stripes alternate red and white and represent the original thirteen colonies that declared independence from Great Britain.
The flag also has a blue canton containing white stars. The stars represent the states in the Union, so their number has changed as states joined the country. The stripes, by contrast, remain fixed at 13 to preserve the connection with the founding colonies.
The first official national flag was adopted by the Second Continental Congress on June 14, 1777. It had 13 stars and 13 stripes, although the arrangement of the stars was not specified. Congress later passed a law in 1794 adding two stripes for Vermont and Kentucky, but the design returned to 13 stripes in 1818.
A common mix-up is to answer 50 because the current flag has 50 stars. The stars count states; the stripes count the original colonies.