Which county in West Virginia borders both Pennsylvania and Maryland?

The correct answer is Preston County, as it is situated in such a way that it shares borders with both Pennsylvania to the north and Maryland to the east. This geographic positioning allows for the unique circumstance of having both states as neighbors, demonstrating Preston County's important location within the tri-state area.

Brooke County, while functioning as a key county, primarily borders Pennsylvania to the north but does not extend far enough to connect with Maryland. Monongalia County also correlates with Pennsylvania but lacks a border with Maryland. Mineral County, located further south, borders Maryland but is not adjacent to Pennsylvania. Thus, it is Preston County that distinctly meets the criteria of bordering both states, showcasing its significance within West Virginia's geographical and historical context.