Did a large number of people have hayfever say 50 years ago and how did they manage their symptoms?

Yes. Immunotherapy. The %age of hay fever sufferers has been rising since around 1800, the beginning of the industrial revolution. Antihistamines have been in common use since ~1950. Decongestant pills and sprays were also used. Escaping to the mountains was a popular treatment that didn't work. Air conditioning (yes they had that then) does work. Allergy shots have been available since 1911 & are safe & effective.
Salt water rinses. Rinsing your nose with salt water is an ancient remedy. Our familiar friend the neti pot is centuries old. You know that anything with a sanskrit name has been in the neighborhood for a good long time.
Yes & Benadryl (diphenhydramine) Hay fever is a 19th century term for allergic rhinitis (ar). "fever" meant inflammation. Ragweed-triggered ar occurs in late summer, the season of cutting hay, and was thought to be due to hay. Ar became common during the industrial revolution. In the mid-20th century treatment relied on sedating antihistamines like benadryl (diphenhydramine). Oral decongestants like sudafed, and immunotherapy (allergy shots).
Hay Fever Management. It is difficult to quantify what would constitute a large number; the incidence is certainly rising and is projected to continue to do so. Antihistamines have been around for many decades - they used to have shorter durations of action and caused more drowsiness. Newer agents are less sedating and last longer. Waiting "until the first frost" was fashionable; we are much better positioned now!