Illinois Golden Ratio

Gerald Thurman felt this sign was a stretch, but it's a sure winner containing Fibonacci's golden rato. This sign also brings Illinois to Road Sign Math, joining the slew of other states that have embraced mathematically significant roadsigns.



Mr. Thurman applies slide-rule-like-deftness to get this winner.

$$\log{\sqrt{85 \times 20}} \approx 1.61265 \approx \varphi$$

This sign is in the northwest corner of