According to Klaus Beyer, Aramaic was a written language as early as the 11th century BCE. Nicholas Ostler's Empires of the World made me realize that together with Classical Chinese, Latin and, more recently, English, Aramaic ranks as one of four most important languages in world history. In his review of the book, Robert Dessaix writes about the spread of Aramaic:
"Aramaic-speakers, for instance, who were nomads from northern Syria, simply swamped the Assyrian empire, which has been happily speaking Akkadian for 2,000 years, bringing with them a superior technology (always a plus): their alphabet, written on papyrus or leather, much handier than cuneiform on clay tablets. In the 6th century BC the Persians found it practical to adopt Aramaic as their official language, so that by the time Alexander the Great invaded Egypt, he found the administration there communicating not in Egyptian but Aramaic, and even Ashoka in far-off India had inscriptions in Aramaic on his monuments.No conquering armies from northern Syria, no settlement of foreign lands, just a bit of 'merger and acquisition' leading to bilingualism in the streets and offices and armies of the Middle East until hey presto! one day anyone who was anyone across half the known world, including eventually Jesus, and millions of nobodies at home as well (that's the important thing) was speaking and writing in an obscure nomadic dialect. Arabic wiped Aramaic out eventually, of course, though invasion and the imposition of a unitary religion but, interestingly, it wiped out only related languages (as Aramaic, and even Egyptian were). It seems that invasion leaves unrelated languages intact and thriving (Persian, Malay, Turkish and so on in the case of Arabic) unless it's accompanied by massive migration and, ideally, a plague or two."
Here's a very comprehensive and instructive Wikipedia article on the ancient and recent history of Aramaic.