None of the bridges in question are of any particular significance but are still a part of the history of the roadway. Most of the bridges were built between 1931 and 1933, replacing earlier level creek crossings. These bridges were subsequently modified and upgraded between 1951 and 1953 to their current condition. While it is sad to see them go, I understand the reasoning behind it. Timber bridges have a limited life span, even in the desert. There are also erosion issues which need to be addressed. Had this roadway continued to be a State Highway past 1972, these bridges would have most likely been upgraded/modified/replaced in the 1980's. With the new bridge rail designs Caltrans has been doing on current State highways, I can only hope that San Bernardino County does the same.
Thank you for the compliment on my site, btw. I've been working on an addition to the site, covering US 466. It is still a work in progress, but the initial framework is at least online.