9 out of 22 were Railroad barons, a couple of department store chain owners, an iron magnate, a fur trader, etc.
Interesting stuff:
They became billionaires by...
* inheritance, plus a stock market boom.
* persuading the government to do your enterprise a truly massive favor.
* being at the right place at the right time: creating an enterprise of truly enormous social utility--and thereafter both retaining the market power to turn a large chunk of that extra social utility into firm profits, and retaining a sufficient ownership share and access to capital markets to turn capitalized firm profits into an enormous fortune.
Characteristics of the billionaire circa 1900...substantial differences in how and where they got their money, with the exceptions of the large # of railroad guys; brutally ruthless; abilities to financially manage the windfalls they received from their machinations; and complete and total corruption.
A great deal of the billionaires owed their wallets to bribes lobbying politicians. As Collis Huntington said:" If you have to pay money to a politician to have the right thing done, is is only just and fair to do it.... If a politician has the power to do great evil and won't do right unless he is bribed to do it, I think... it is a man's duty to go up and bribe"
I'm sure we can all draw some analog's to a number of todays situations...