I just found this group. I have a old farm light plant and have studied them. Recently I have been learning about the fixtures and wiring.
I have a few books from 1919 and 1920 farm and home wiring. BTW They suggest a light on the porch. (8CP 10 watt) They don't give the reason but it is clear from the illustrations that it is so your neighbors can see that you have electricity.
A friend of mine is renovating his farm home, which before rural electrification, had a Delco plant, and there are some remnants of the system still in the buildings.