The document summarizes 10 key steps in the development of the European Union:
1) The Treaty of Paris in 1951 established the European Coal and Steel Community among 6 countries.
2) The Treaty of Rome in 1957 formed the European Economic Community and introduced policies like a common market.
3) In 1973, the UK, Ireland and Denmark joined in the first expansion of the EU.
4) Greece joined in 1981, and Portugal and Spain joined in 1986 in the Iberian Expansion.