I found this button in suburbia on a piece of land that was once a farm dating back to at least 1835.
It measures 30 mm in diameter.
Any info to help date this find would be appreciated.
Button collectors call that type a brass 1-piece "flatbutton." The specific type you found, being a simple disc of stamped brass with a loop brazed onto its back, was manufactured from the 1790s until about 1840. They were made for use on civilian coats & jackets, although a few did get used on Militia uniforms. Yours, which has a bit of decorative design around its edge, was strictly civilian-usage.