When the current state highway numbering system was first posted in January 1964, SR 403 began at Altoona and headed west, then north, then NE to Jct US 830 at Rosburg, where SR 403 ended. In 1968, US 830 through Rosburg was renumbered SR 4. SR 403 was dropped from the state highway system effective April 1, 1992.
Before 1964, SR 403 had been SSH 12C.
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