But, you may ask, if the two departments [i.e., federal and state] should claim each the same subject of power, where is the common umpire to decide ultimately between them? In cases of little importance or urgency, the prudence of both parties will keep them aloof from the questionable ground; but if it can neither be avoided nor compromised, a convention of the States must be called to ascribe the doubtful power to that department which they may think best.
Thomas JeffersonThe expedition of Messrs. Lewis & Clarke for exploring the river Missouri, & the best communication from that to the Pacific ocean, has had all the success which could have been expected.
Thomas Jefferson