mesta (māˈstä) [key], association of Spanish sheep farmers, formed to regulate sheep raising and to prevent cultivation of pastureland. Its date of origin is uncertain, but by 1273 Alfonso X of Castile formally recognized its long-established privileges, which were confirmed and extended by his successors. The mesta gradually escaped local jurisdiction and came under direct supervision of the crown. It prospered, especially in the 15th and 16th cent., by exporting wool from its highly prized Merino sheep. The mesta yielded large revenues to the crown, but its monopoly of large areas of land exhausted the soil and contributed to the economic decline of Spain by preventing intensive agriculture. Attacked by reforming ministers in the 18th cent., it was not abolished until 1837.