What material was commonly used for historic wood siding in warm, humid climates?

Old growth cypress is the correct choice because it is a durable wood that has been traditionally favored for use in warm, humid climates, especially in regions like Charleston. The unique properties of cypress wood, including its natural resistance to decay and insects, make it particularly well-suited for the environmental conditions found in these climates.

Cypress also has a beautiful natural grain and tends to hold up better against the elements compared to other types of wood. It can withstand the humidity without warping or splitting, which is crucial for maintaining the integrity of historic buildings over time.

In contrast, while redwood and oak have their uses, they are not as commonly associated with the historic buildings in humid climates. Pine wood, although used in various applications, tends to be less durable than cypress and more susceptible to the effects of moisture. Therefore, old growth cypress stands out as the material of choice for constructing wood siding in these specific climates.