It was not recorded on the banzuke until 1890 and was not officially recognised as sumo's highest rank until 1909.
The first list of yokozuna (with 17 names in total) was compiled by the 12th yokozuna Jinmaku Kyūgorō in 1900 but was not regarded as official until 1926 when it was published by the newly formed Japan Sumo Association and updated to 31 names.
Two consecutive tournament championships or an "equivalent performance" at ōzeki level are the minimum requirement for promotion to yokozuna in modern sumo.
The longest serving yokozuna ever was Hakuhō, who was promoted in 2007 and retired in 2021.
[1] The number of top division championships won by each yokozuna is also listed.