| State: | WA |
| Type: | SR |
| Route: | 523 |
| Alternate Name: | 145th Street |
| Section: | 727 |
| Map Custom: | yes |
| Map Notes: | A map of northern Seattle with SR 523 highlighted in red |
| Length Mi: | 2.45 |
| Length Round: | 2 |
| Length Ref: | [1] |
| Established: | 1991[2] [3] |
| Direction A: | West |
| Terminus A: | in Seattle and Shoreline |
| Junction: | in Seattle and Shoreline |
| Direction B: | East |
| Terminus B: | in Seattle and Lake Forest Park |
| County: | King |
| Spur Type: | I |
| Spur Of: | 5 |
| Previous Type: | SR |
| Previous Route: | 522 |
| Next Type: | SR |
| Next Route: | 524 |
State Route 523 (SR 523, named 145th Street) is a short Washington state highway located on the city limits of Seattle, Shoreline, and Lake Forest Park in King County. The road itself runs 2.45miles east from past (I-5) and ends at ; the highway was first established in 1991, but the roadway from I-5 to 5th Avenue Northeast was once the northern section of from 1937 until 1964 and later from 1964 until 1991.
State Route 523 (SR 523) begins at an intersection with and North 145th Street at the northern Seattle and southern Shoreline city limits;[4] at the SR 99 intersection, the highway is named 145th Street.[1] From its western terminus, the roadway travels east to 1st Avenue NE, where SR 523 becomes Northeast 145th Street, which the road keeps until its eastern terminus.[1] The highway travels 0.2miles east to interchange with (I-5), where the northbound ramps are accessed through nearby 5th Avenue Northeast.[1] [5] After the I-5 interchange, the road forms the northern boundary of the Jackson Park Golf Course and later continues to at the northern Seattle, southern Shoreline and western Lake Forest Park city limits.[4] The SR 523 / I-5 interchange was used by an estimated 28,000 motorists daily based on annual average daily traffic (AADT) data collected by the Washington State Department of Transportation.[6]
145th Street was paved by the King County government between 1934 and 1935.[7] The Washington State Legislature first established a state-maintained highway on a section of present-day SR 523 in 1937, with the establishment of (SSH 1J), which ran from Downtown Seattle to (PSH 1) in North Seattle, via the current 0.052NaN2 long section of SR 523 from I-5 to 5th Avenue Northeast.[1] [8] During the 1964 highway renumbering, SSH 1J became and PSH 1 became I-5;[9] the northern terminus of SR 513 became the current SR 523 / I-5 interchange.[10] In 1991, the northern terminus of SR 513 was moved south to its current location, Magnuson Park and SR 523 was established.[2] [3]