The STH 70/101 duplex has existed since 1949, when 70 was extended from STH 55 south of Alvin eastward to its present terminus. STH 101 has existed since STH 14 (now US 8) was rerouted at Armstrong Creek to end at STH 57 (now US 141) south of Pembine in 1923. The STH 47/182 duplex was originally a CTH-F/CTH-G duplex, before G was replaced by 182 in 1948, and 47 replaced F in 1952. Other duplexes to a common terminus include STH 71/108: co-designated since 1923 (108 was designated in 1919 and 71 was extended from Elroy to Melrose four years later); and STH 48/STH 87, also co-designated since 1923. As for STH 20, I think it should have ended at STH 32 and not been co-designated together. I'm not sure if 20 was also co-designated with 32's predecessors: STH 15 (1923-1930), STH 17 (1917-1926), and STH 42 (1930-1951). It would depend on whether those routes followed the same alignment through Racine as STH 32.