At what minimum height above terrain does a vertical structure need to be indicated on a sectional map?

Question

I recently drove by what seemed like an unusually tall structure and used Google Maps satellite view, its distance measurement tool, and basic trigonometry to calculate that this building (some kind of grain silo at a poultry processing plant) was 175 feet tall above the ground.

But, it does not show up on the sectional map. Other nearby structures, mostly 300-350 feet or greater, do indeed show on the map.

At what minimum height above terrain does a vertical structure need to be indicated on a sectional map?

Answer 1

Refer to Aeronautical Chart Users Guide 2017. There are 351,148 obstacles in the database. Generally it is when ”a manmade obstacle is 200' above the highest terrain in the quadrant”. However, “in high density areas like city complexes, only the highest obstacle is represented on the chart”. Then they do the calculations below to show the obstacle on the chart.

Answer 2

I'll accept JScarry's answer, but here's a clearer image of the map shown in his/her image:

Courtesy of Skyvector.com.

P.S. I LOVE sectional maps - lots of interesting info there.