My thought would be that we should defer to the federal government's official name for the canyon rather than the city's official name. And also, when I talk to people about this canyon, every single person I know refers to the canyon as "Bells" rather than "Bell".

So my preference would be to keep the canyon, trail, and reservoirs labeled as "Bells", with the alt_name field specifying "Bell". But since the trailhead is signed "Bell" in the field then we should keep the trailhead as "Bell" with the alt-name "Bells". Any thoughts?