Hence I believe it can be argued that 1957 marks the birth date of the modern motorcycle helmet. As helmet testing and development along with head injury research developed a body of data, helmet legislation began to be considered sporadically across the USA through the 1960's and '70's. In Canada in the late '60's and in the UK in the early '70's.
Helmet development has continued, arguably driven in part by the Snell Memorial Foundation's policy of revisiting helmet standards every 5 years. The quality and level of protection we get from our helmets today is the result of hardly more than half a century of development, and contributions from almost every branch of science.