The Primary State Highway (PSH) numbers consisted of one and two
digits. Some PSH routes had branches that were themselves PSH routes. Such PSH
branches were posted in the field with the same number as the trunk but had an
additional identifier in Department of Highway records. Thus PSH 1 RE (Renton
Branch) was posted in the field as State Highway 1. This route is now Interstate
405. The PSH 1 trunk, the Pacific Highway, was posted as US 99 and is now
Interstate 5.
