I think compared to families starving, having lots of kids is definitely prosperous. From what I can tell from ancestry, they prospered in the traditional sense too though. My third great grandfather was apparently a blacksmith who got a job at a mine, then went to Oregon territories during the gold rush, and came back to the Midwest and bought tons of land. Like hundred of acres. I'm thinking maybe he opened a shop selling shovels or something but it's a total guess. Not many get rich off finding gold but maybe. Hard for me to really track what happened with him because he sold all his land to his daughter for almost nothing and his son (my great great grandfather) moved south.