Please answer a question about the following article about St. John%27s, Newfoundland and Labrador:

Starting as a fishing outpost for European fishermen, St. John's consisted mostly of the homes of fishermen, sheds, storage shacks, and wharves constructed out of wood. Like many other cities of the time, as the Industrial Revolution took hold and new methods and materials for construction were introduced, the landscape changed as the city grew in width and height. The Great Fire of 1892 destroyed most of the downtown core, and most residential and other wood-frame buildings date from this period.

What are wharves in St. John's constructed out of?
wood