When the current state highway numbering system was first posted in January 1964, the highway that later became SR 431 was designated as SR 831. SR 831 began at Jct US 830 in Kelso and headed NE to I-5/US 99 Exit 40. When US 830 west of I-5 was redesignated as SR 4 in 1968, SR 831 became SR 431. Effective April 1, 1992, SR 431 was dropped from the state highway system. If former SR 431 is not significant enough to be a state highway, why do the guide signs on southbound I-5 still direct traffic headed towards Longview via former SR 431 rather than signing the exit simply as N. Kelso Ave?
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