Some of the first tree stands were actually used in WWII as sniper platforms I have read

Look up 'Andy's' tree stands or Andy Tree Stand......... They were some of the first...

Thats the best leads I can give you....... from what I have read these are accurate. I was told the Andy Stand originated in Jacksonville Florida

I remember building my first climber in aprox 1980 after reading an article in Field n Stream or outdoor life / Sport Afield (one of them)