Ooops! Have just realised I didn't say that in my original post I was only answering the 'in the U.K.' bit! Re Grand Central Airport Glendale, I've got a completion date of 1928, no month I'm afraid. What you say regarding what is a hard runway is a good point. I seem to remember that the RAF, for instance, were using oil consolidated sand runways in the Middle east in the mid 1920's. Think this is stretching the point though and we're almost certainly looking at Tarmac/Asphalt/Concrete here.
Spiney