Counterfeit money has been around for as long as genuine money has. Before there was a national currency, each bank printed their own bills. There were over 7,000 varieties of real bills and 4,000 varieties of counterfeit bills. In 1863 a national currency was designed and implimented but counterfeit money was still extremely easy to make. In 1865, the Secret Service began investigating suspected counterfeiters.
The Secret Service seized $209 million in counterfeit money in 1994. They believe that 90% of all counterfeit money is confiscated before it reaches circulation.
Counterfeit US money isn't just printed in the US. Iran and Syria are also believed to be printing the US bill.
Abraham Lincoln is found on the front of the $5 bill. On the back of the bill is the Lincoln Memorial.