Prefer contemporaneous, specific records
A dated floor plan naming a maternity ward is stronger evidence for the ward than a modern hospital history. A property parcel or directory from the correct year can be stronger for an address than a present-day business listing.
Use maps as spatial evidence, not magic
Sanborn maps can be extraordinarily detailed, including building footprints and uses, but coverage varies by city and year. USGS maps provide a different scale and purpose. Combine them rather than treating either as universal.
Sources: Library of Congress — Sanborn Fire Insurance Maps · U.S. Geological Survey — Historical Topographic Map Collection
Corroborate when the claim gets more precise
City-level claims may need one strong source. Building- or room-level claims deserve corroboration because small mistakes become proportionally more important.
Record the losing hypotheses
If two buildings were plausible and one was ruled out, keep that note. Negative evidence can prevent the same ambiguity from being reintroduced later.