When the current state highway numbering system was first posted in January 1964, the highway that was to become SR 237 was posted as SR 537. This highway began at Jct SR 536 between Fredonia and Whitney and headed north to Edison, then east to Jct SR 11. After the North Cascades Highway was completed, the SR 20 designation replaced the SR 536 designation west of Fredonia. Since SR 537 no longer connected with another 500 series highway but did connect with SR 20, the SR 237 designation was substituted for the SR 537 designation in 1975. Effective April 1, 1992, SR 237 was dropped from the state highway system.
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