I-109 (preliminary numbering)  California (link)

On April 1, 1958, California submitted to AASHO a numbering plan for its proposed interstates, including 3-digit spurs numbered in the low 100s and not associated with their parent interstates. Interstate 109 was the proposed number for what became I-280. [1]

This number was not compliant with AASHO's numbering convention and was rejected.

On August 7, 1958, California had bought in to the system and submitted I-280. This was approved, along with the rest of California's original interstate highway system, on Nov. 10, 1958. [2]

(Earlier in 1957, the state had submitted I-3 for this highway.) [1]

See also:

• California Interstate Route Numbering (Stephen Summers)
• California Interstate Types and History (Daniel Faigin)

Sources

1. Summers, Stephen. "Interstate system route numbering." http://www.nwindianahwys.homestead.com/INTER_MAIN.HTML. (29 May 2003)
2. Faigin, Daniel. "California Highways (www.cahighways.org): Interstate Highway Types and Interstate History." http://www.cahighways.org/itypes.html (29 May 2003)