What is this metal pole in my backyard?

Question

Can someone help identify this old metal pole in the backyard? It's very tall and seems to have a a hookup for water supply. The house was built in the 1940s and is located in the California East Bay hills

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Answer 1

I really like "what is this old thing left from a previous time" questions. This is just a guess, but here it is.

https://www.rockridgewindmills.com/photo-video-gallery/early-california-windmill-photos/#rockridgewindmills-1/0/Redwood_Windmill_Water_Tower.jpg

What you have left was once the center pole from a water pumping windmill. You must imagine the windmill and the wood frame, and the water tank that was once filled by this windmill. But a windmill and a water tank in the Bay area seems right, from when this was still an agricultural area.