Originated as a natural bud sport on a Thompson Pink tree growing in McAllen, Texas, discovered by Albert E. Henninger in 1929. Thompson Pink itself was a bud mutation of Marsh Seedless, making Ruby Red part of the Marsh-derived grapefruit lineage. The mutation was first noticed when fruit with an unusually pink to red rind blush and deep red flesh appeared on a single limb. Subsequent fruit from the same limb confirmed the stability of the trait, and budded progeny reproduced the coloration. Ruby Red was formally patented in 1933 (US Plant Patent No. 53), becoming the first citrus variety ever to receive a U.S. plant patent. Ruby Red marked the first commercially successful transition from pale pink to true red grapefruit, forming the foundation for later red-fleshed varieties such as Rio Red and Star Ruby.