Analysis of information sources in references of the Wikipedia article "Transportation in California" in English language version.
State routes can be identified by the green State Highway Route shield, which is in the shape of a spade in honor of the California Gold Rush, and bears the route's number
In the 1960s, green and white CA-99 signs that resemble miners' spades replaced the black and white U.S. 99 shields
In the 1960s, green and white CA-99 signs that resemble miners' spades replaced the black and white U.S. 99 shields
State routes can be identified by the green State Highway Route shield, which is in the shape of a spade in honor of the California Gold Rush, and bears the route's number
