Which US state has no speed limit?
Speed limits in the United States
Montana
Upon that repeal, there was effectively no speed limit on Montana's interstates for daytime driving (the nighttime limit was set at 65mph) from 1995 to 1999, when the state Supreme Court threw out the law as "unconstitutionally vague."[83] The state legislature enacted a 75mph daytime limit in May 1999.[84]