Best I can tell, Newport pro William Davis did the original course, Ross reworked it in 1915 and Tillinghast added all of the (good) holes across the road along the water, plus tinkered with the bunkering of the holes that remained, in the process taking at least seven of the Davis/Ross holes out of commission.
Interestingly, there is a stunning b&w aerial of the place hanging on the clubhouse wall, gifted by President Eisenhower, that shows an incredible array of Tillinghast-styled bunkering. I forgot to inspect the cars in the parking lot to determine their vintage on the aerial, but I do know that Eisenhower played there during his presidency. Ron Forse, who is on retainer (sort of) by the club might know more. After this event, they certainly will need to rebuild all of their bunkers and install proper drainage. Of course the club might not have incentive, since there's no reason to think the USGA will return until the next century - if they keep to their current schedule (1895, 1995, 2006).