Creating origami with paper money may have begun as early as the 1800's, but it didn't become popular in the U.S. until the 1950's. The idea really caught on when gift-givers began realizing how fun and easy it was to inject a little creativity into the routine tradition of exchanging cash. For instance, folding bills into the shape of Christmas trees during the holiday season can add a festive feel that most recipients would never expect.
Select a crisp dollar bill. Fold it in half lengthwise with the face side inside the fold. Unfold it and lay it flat.
Fold the bill in half again but in the other direction (face still inside fold) with the short ends lined up and the eagle-with-shield facing up.
Fold down the eagle side part way, creasing it horizontally next to the letter "E" in the word "ONE."
Turn down the two top corners of the last fold, forming tiny right triangles separated by a 1-inch space.
Begin creating the tree trunk by folding the lower left corner of the bill toward the right, letting the right triangle turn into a roof-shaped triangle. Repeat this process on the right side of the bill. The fold from step 3 now is divided into thirds vertically.
Make another set of triangles. Start at the midpoint of the bill's top edge to fold down the top two corners of the bill until they touch. Start at the midpoint of the bill's top edge. This is the beginning of the tree's peak. The bill's shape now is similar to the spade on a playing card.
Transform the spade into a pine tree by folding two more long, shallow triangles stretching from the peak of the tree to the bottom right and left corners of the spade. Flip the folded bill over to see the tree, then tape it to a package or card.