Here is a photo of the cover of the City of Corvallis'
Bicycle Ordinance & Handbook from about 1971. I think this is where a lot of people who post against helmets want us to go. There is only one problem with this, and that is that when you look at the number of bicycle fatalities during that time, they are higher in the USA than today. But look at where other countries are in their fatalities. It is not that they wear or don't wear helmets, but that the bicycling infrastructure is so different that their fatality rates are lower.
(From the
Bicycling and Walking in the United States, 2012 Benchmarking Report.)
John