Mueller Tunnel

On the Mt. Lowe trail (road), San Gabriel Mountains, southern California. The "U.S.F.S." on the arch stands for US Forest Service. The road is located in the Angeles National Forest--evidently forest fire protection was a wartime priority, such that they bothered to build the tunnel just after the US entry into WW II (note the 1942 date above the portal). In theory the road is still open to emergency vehicles, but they'd have to move some rocks! It's now a hiking/horse/mountain biking trail primarily.