Oregonian rhymes with:
patagonian, gorgonian, patagonian, amazonian, andonian, apollonian, babylonian, bostonian, caledonian, devonian, draconian, estonian, gorgonian, houstonian, jacksonian, jeffersonian, melkonian, newtonian, patagonian, plutonian, simonian, smithsonian, usoniam, washingtonian
Oregonian sounds like:
oarsman, oregan, oregano, oregon, organ, organum, orgasm, origin, orkem, orkin, orkney, orrison, orsini, orsino, orson