History
OpenStreetMap welcomes data about old buildings, canals, and other features that exist into the present day. However, in general, the history of the world is out of scope for OSM. We don't map historic events and historic features that no longer exist, and we even delete features once they're gone and become nonexistent features. This is a consequence of the project's approach to verifiability, which prizes objectivity and direct observation when possible.
A historical site or other feature of historical significance is usually tagged with historic=* or heritage=* along with other tags characterizing the feature. Specialized maps such as Historic.Place and HistOSM make it easy to find these historically significant features.
In some limited situations, we do map defunct features, using lifecycle prefixes and other lifecycle concepts to distinguish them from extant features. For example, a building footprint may remain visible on the ground long after the building is demolished. Or it may leave a digital trace in some of the imagery sources we regularly consult, requiring a temporary placeholder to keep mappers from getting confused and incorrectly reviving it as an extant building. A ghost sign that no longer serves the purpose of identifying a shop can still be mapped as the sign itself, using advertising=sign, while an old name=* tag on the associated building can indicate the original referent. Although OSM doesn't aim to comprehensively track the history of a real-world feature, some features have start_date=* tags based on visible inscriptions or signs. Demolished railways have been a frequent flashpoint for controversy, with debate about how to model the vestiges of dismantled railways, whether to map the enduring effects of a former railway on subsequent development, and whether to infer a railway line from the fragments of extant features.
OpenHistoricalMap is OSM's companion project for deliberately mapping the history of the world, from the earliest known origins of features to the present day and even a little beyond. OHM aims to cover anything no matter how historically significant or insignificant. The project uses software based on OSM but maintains a separate database, because mapping the past often requires different methods and perspective than mapping the present. History-minded mappers can contribute to both projects in tandem.