100% agree with respect to riverboats. Riverboats provided transportation and that's it.

Poker games were run by the passengers. Professional gamblers would bring all the necessary paraphernalia necessary to run a game.

Some clubs did have ivories. The Madison Square club in NYC had ivories (MSC chips on my website)

I have a set of 4 ivories that I am pretty sure we're used in a Saloon in Utah. Pictures as well as newspaper articles are shown on my website: http://www.oldpokerchips.com/IVORY/DanielClay.htm

Finally, the ivory chip that is nearest and dearest to my heart:

I have several newspaper articles mentioning that ivories were used at this illegal club. Great reading on this page:
http://www.oldpokerchips.com/IVORY/24HanoverSt.htm