Long 1x6 planks were a standard choice for horizontal siding. This created the clean, "long feature" lines characteristic of Late Victorian and early Craftsman cottages.
Before plywood, 1x6 boards were nailed diagonally across floor joists or wall studs to provide lateral stability to the frame. 1899 1x6
Whenever possible, preservationists recommend stripping and refinishing original 1x6 baseboards rather than replacing them, as the dense grain of century-old wood is difficult to replicate. Long 1x6 planks were a standard choice for horizontal siding