Beef and pork are another example I can think of though, this has to do with specific cuts and quality for various markets.

There are also regional specializations. Like, BC has a substantial amount of Western Red Cedar which the north western states can’t meet the demand for alone.

We also send raw materials to be processed by mills in the USA. This isn’t as common as it once was. Then we also send lumber which US mills process. Some examples would be fir boards would are turned into flooring, window sash, stair treads, etc. BC produces a ton of material like this which is fodder for all kinds of mills, large and small. We try to keep that business here, but we tend to mostly dimension raw materials for export, rather than actually mill them and add any meaningful value.

We import a lot of hardwood lumbers from the USA. I’ve personally bought and milled American hardwoods for furniture in my home. We have beautiful hardwoods in Canada, but there are a lot in the USA we simply don’t grow, or at least not commercially.