The first appearance of "Cap" dates back all the way to March 1941, with the first issue of Captain America Comics #1, published by Timely Comics (the precursor to the well-known Marvel Comics). Captain America was created by writer Joe Simon and legendary comic book illustrator Jack Kirby, who is also credited with creating the Fantastic Four and the X-Men.
The initial publication was very popular during the second world war because it depicted a patriotic solider fighting the evil Axis powers. At a time when real life was bleak, and people looked for hope in everything, Captain America kept both military moral high and inspired those at home to work harder to support their troops.
Captain America was also the very first Marvel Comics character adapted for film with the release of a 1944 movie serial. These were the equivalent to our modern TV series - TV was not yet commonly available for home use - and each episode lasted about 30 minutes and ended with a cliffhanger.
I have high hopes for Captain America, and going by the trailers it shouldn't be too much of a disappointment. Then again, the Green Hornet promos promised far more than the film delivered. Still, I'm holding my breath ...