The modern-day U.A.E.'s only real wealth came from pearl diving, but this industry dried up in the 1900s and the region returned to nomadic Bedouins living in poverty. In the early 20th century this changed again when oil was discovered and export of the good began in the 1960s. Abu Dhabi focused their economy of this good, while Dubai focused on being a trading center and port city as the rest of the Emirates fell into obscurity.
In 1971, Abu Dhabi's sheikh, Zayed worked with the other gulf coast emirates' sheikhs to create a united nation as the British discussed giving up control over the region. Most of the emirates along the coast joined (Bahrain and Qatar didn't) with Abu Dhabi acting as the country's capital. Since then, power has been primarily held in the emirates of Abu Dhabi and Dubai, however all the emirates have benefited from this union.
Today the United Arab Emirates has quickly become one of the most progressive and modern countries in the world as oil money and tax-free trade through Dubai have made the country a meeting place for the entire Arabic speaking world as it also attracts workers and tourists from nearly every country in the world. Today the country's residents primarily consist of foreign non-citizens (over 80%), but the local population financially benefits from their work.