I am trying to buy a house in Missouri, date was shown as 1957, which doesn't seem right to myself or the real estate agent. My house also has doorknobs with keyholes like yours (as I remember in grandmothers old house) - and has a capped cistern in back - which was used before the area had public water lines. My house is located in Jefferson county. I have tried to find online when door locks like these stopped being put in houses. I also noted solid wood interior doors.

Try looking at the inside of the toliet tank or lid. They often have the month/year stamped in them if they are orginal.

Also the bottom of any orginal sinks or bath basins.

The tax assesor office will usually have that information and in some counties it is online.

It would help to see more of the interior --molding, lighting, etc., but I would guess around 1920.