Alabama's "Old Rotation" (c. 1896) is the oldest, continuous cotton experiment in the world and the third oldest continuous field crop experiment in the same location in the United States. It was placed on the National Register of Historical Places in 1988 and is celebrating its centennial this year. It is the only surviving, 19th century experiment that demonstrates the beneficial effects of rotating cotton with other crops and including winter legumes as a source of nitrogen. Where no N is included in a rotation, low cotton and corn yields continue to decline for 15 to 20 years until a relatively stable, low yield is reached. Annual N removed in cotton seed and lint (12 lb/acre/yr) is approximately that which would be expected to be available from atmospheric deposition and non-symbiotic fixation. Including a winter legume cover crop (crimson clover and/or vetch) has produced long-term yields equal to or greater than those achieved from applying 120 lb. N/acre/yr as ammonium nitrate to non-irrigated cotton. There is little yield advantage to long-term rotations for cotton, but there may be some risk advantages. Sustainable productivity research conducted using long-term records from the Old Rotation has shown that (1) continuous cotton production is sustainable, (2) output per unit of input is higher today than when the experiment began, (3) long-term productivity occurs in unexplained cycles, and (4) the most important technological advancement in sustainable cotton production was the introduction of the mechanical cotton harvester.