Historical archaeology is a form of archaeology dealing with places, things, and issues from the past or present when written records and oral traditions can inform and contextualize cultural material.
These records can both complement and conflict with the archaeological evidence found at a particular site.
While they may not have generated the records, the lives of people for whom there was little need for written records, such as the working class, slaves, indentured labourers, and children but who live in the historical period can also be the subject of study.
In practice, however – mainly in the Americas – historical archaeology refers to the modern, post-1492 period, which in Europe is often referred to as post-medieval archaeology.
One of the more unfortunate ones--which is certainly not true but which should be mentioned--is that historical archaeology is the most expensive way in the world to learn something we already know.