Almost all data (perhaps we could say evidence) that is collected in Historical archaeology has a spatial component. 

Historical archaeology deals with a modern world that is global. A domestic site, although full of interesting and important artefacts that may be studied alone, is also important because of its relationship to an Industrial site, (the location of workers homes) etc. Complex sites such as urban areas, require examination of spatial data to help resolve relationships, ethnicity, groups, status and linkages.

What does this spatial component tell us?

Spatial data or observing our data laid out in space, can allow us to observe and answer questions about Relationships, associations and connections. 

Transport, Commodities (from resource to production to consumer), activity areas, Groups, distribution of disease and  Settlement patterns are elements of Historical Archaeology that can benefit from examining spatial data.

Any study that involves landscapes must take into account spatial relationships.

Visual representation is a powerful tool. Humans respond well to the visual. Simply displaying our data on maps can help convey relationships.