Here is a view of Robinson in the foreground, and Mammoth in the background. These mining camps were located southwest of Eureka in Juab County, Utah.
It is unfortunate that this letter has no first page, since we would know where it was written and when; we've also lost a third of it's content. From the context it's plain that Milt and Maggie have not yet married. It is likely he wrote it from the boarding house at Robinson, probably early Spring, 1911.