We just removed the old thermostat from our 1911 house. I do not think it is original to the house, but it is at least 20 years old. We don't know if we can throw it away or need to recycle it at an environmental agency. Please advise.
Thank you!:)

It is very possible, that thermostat has mercury in it, and should not be thrown in to the trash. Call you local disposal company, they should know where you can take it. Around here 2 times a year they have a solid waste day when you can take items like that to one of several sites for proper disposal.

There is also a good chance you might be able to drop it off at a local HVAC supply house.