: I'm not sure on this, but I think what they do is kiln-dry it and then leave
: it out in the rain.

From what I've seen, that seems about right, though I can't figure out why they do that.

: Dimensionally it seems pretty stable, and it's
: finished to 1-1/2 x 3-1/2, rough on one side.

Interesting. Around here, all I usually find is S4S 2x4's that are typically 1 3/8" x 3 3/8". Pretty skimpy. On the other hand, 4x4's usually measure 3 1/2" square, which gives me blanks that are ~1 5/8" thick after re-sawing and running them through the planer.

: The resawn strips dried in a
: day at 110 degrees. The 2x4 is still in there, three days later, and I
: cant feel a weight difference. It'll hit the table saw pretty soon.

I've seen significant drops in weight, but only with blanks that were very heavy (wet) to begin with. When I find a light piece, it usually means it's dry and the weight doesn't change much over time.