No ships were there at the mouth of the Columbia River to resupply them or to take them home. They got to thinking, winter-time was coming. We're going to have to walk back home. We can't make it back home without salt. They were forced to spend most of the winter there distilling salt from the ocean so they could make it back home.
Salt is vital to life.
We can't live without Salt. Our body has about eight ounces of salt in it. Enough for a big salt shaker. Salt regulates the water in our cells, it aids muscle contraction, nerve impulses, and heartbeats. Without vital salt, we would go into convulsions and die.