Eventually, the Arrow Rock Dam does get built, but Oliver doesn't end up getting any credit for it. It seems like the government just took control of the project at some point.
The family ends up staying in the canyon camp for about five more years. It's actually a pretty happy time for everyone involved.
So, let's stop this time jumping and settle in to September 1883.
The whole crew is chilling beside the water, enjoying a roaring campfire. They've just failed to secure financial backing once again. This time it's especially bad, though: without money, they won't be able to do any more work for the rest of the year.
Oliver doesn't even have enough cash to pay Frank and Wiley anymore. Without hesitating, both men volunteer to keep working for free.
That's when someone gets the bright idea to spend the winter building a house. That way, Frank and Wiley can move into the shack for the winter, while the Ward family can be someplace that's a little more comfortable.
There's one problem: Susan is the only one with cash right now. Although Oliver doesn't want to use it, she convinces him by saying that she'll pay for the house now but "sell it back to the company [...] for twice what it costs" once they get back on their feet (7.3.55).
Next, we see a letter to Augusta detailing the construction of the house. Everyone is having a jolly good time, despite the brutal Idaho winter. Even Charley Wan has stuck around.