<P> From there, the route passes mostly east--west through Jackson and Jones counties . There are short concurrencies with SD 73 (from the west entering Kadoka) and SD 63 in Jackson County . Interstate 90 crosses the Central Time / Mountain Time Zone boundary on the west edge of Jones County . Then at Murdo, a concurrency begins with U.S. Route 83 at exit 192 and continues to exit 212 . It is in Lyman County, at exit 212 in Vivian, that the highway provides its closest link to the capital of Pierre, along US - 83, some 35 miles (56 km) north . The road crosses the Missouri River at Lake Francis Case, between the towns of Oacoma and Chamberlain, also crossing into Brule County . I - 90 Business Loop runs from exit 260 at Oacoma to downtown Chamberlain across the Missouri River on the nearby Chamberlain Bridge, and returns to I - 90 at exit 265 . Beginning there is a short concurrency with SD 50 heading to Pukwana, and also in Brule County is another short concurrency with SD 45 starting at Kimball . </P> <P> I - 90 then continues through Aurora County (connecting to White Lake and Plankinton), Davison County (where Mt . Vernon, Mitchell and the Corn Palace are located), Hanson County (Alexandria), and McCook County (Salem). Then comes the state's most populous county, Minnehaha . After passing the communities of Humboldt and Hartford, the interstate intersects the only other major interstate in the state, Interstate 29, at Sioux Falls, the largest city . Just east of Interstate 29 is where Interstate 90 meets the northern terminus of Interstate 229 . East of Brandon and northeast of Valley Springs, it then ends its trip through South Dakota of 412 miles (663 km) before entering Minnesota and Rock County, just west of the towns of Beaver Creek and Manley . </P> <P> Since April 2015 the speed limit is 80 miles per hour (130 km / h), except it is 65 miles per hour (105 km / h) between I - 229 and Marion Road in Sioux Falls; or through Rapid City . The speed limit remains 75 miles per hour (121 km / h) between Rapid City and the Wyoming state line . </P> <P> The South Dakota section of I - 90 is defined at South Dakota Codified Laws § 31 - 4 - 184 . </P>

What is the speed limit on i 90 in south dakota
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