Gilan was a major producer of silk beginning in the 15th century CE. As a result, it was one of the wealthiest provinces in Iran. Safavid annexation in the 16th century was at least partially motivated by this revenue stream. The silk trade, though not the production, was a monopoly of the Crown and the single most important source of trade revenue for the imperial treasury. As early as the 16th century and until the mid 19th century, Gilan was the major exporter of silk in Asia. The Shah farmed out this trade to Greek and Armenian merchants and, in return, received a handsome portion of the proceeds.