That's a good question. I'm sad there isn't much response from the Historians. My grandfather worked for a short time in a chinese restaurant in los angeles after WWII, and he would take me and the family to local ones, so this topic is one i have an interest in, although i am NOT A HISTORIAN (sorry to the mods).

The earliest Google Digitized Newspaper search hit I get is this from 1970: http://news.google.com/newspapers?nid=2277&dat=19700622&id=MWwmAAAAIBAJ&sjid=-VQDAAAAIBAJ&pg=1837,6113576

Anohter relevant point is here: http://www.sacbee.com/entertainment/living/travel/article4171477.html there is a link to the Oroville CA restaurant Tong Fong Low, which opened in 1912. You can see that they were endorsed by the locals at a grand re-opening, on Robinson Street, which i have not been able to date (apparently, their phone number was "506" -- only three digits!!)

Finally, I can recommend the books Fortune Cookie Chronicles by Jennifer Lee, and Chop Suey by Andrew Coe. I hope that can help you! Good Luck!