The euro was introduced on the first of the year in 1999. It replaced the currencies of 11 member states. As of February 2015, It is accepted in 17 of the 27 member states of the European Union.
In part, the introduction of the euro was a result of the Maastricht Treaty, which effectively unified the 12 original member counties in defense, currency and citizenship.
The euro was first introduced as an accounting and cashless payment option in 1999, but was circulated as paper money in 2002.Learn more about Currency & Conversions