His name is Scott Weaver, and he started the project almost forty years ago, in 1974. It's called "Rolling Through the Bay." As you can see by the image, it isn't a scale model of the city itself, but rather a sculpture of many of its landmarks.
Weaver has included four "tours" of the city in his sculpture in the form of ping pong ball tracks that roll through the landmarks. The whole project took him about 3000 hours over the 35 year period, and though he claims to have used only Elmer's glue, he has used many kinds of toothpicks.
According to Weaver, many of his friends and family collect toothpicks in their travels for him. Some of the toothpicks that make up the trees in Golden Gate Park are from Kenya, Morocco, Spain, and Italy. He had been working on the project for so many years that some of the toothpicks he used are from West Germany, which ceased to exist in 1990. He even used toothpicks from his wedding.