They're near the top left corner. On a good monitor one is waving at you.

The reinforced concrete Donner Summit or Rainbow Bridge has a date stamp of 1925. It opened the following year, just as named highways were replaced by the numbered system.

This routing, though a 7% grade, is a big improvement. Traces of the earlier road, based on an old horse and wagon trail, remain. And I-80 isn't far (enough) away.