It could be crossed at any point; and the same rapid current which made it a matter of extreme difficulty for any power at the mouth of the stream to send reinforcements up against the current would have greatly facilitated the movements of the Ohio, Kentucky, and Tennessee levies down-stream to attack the Spanish provinces.

In the days of sails and oars a great river with rapid current might vitally affect military operations if these depended upon sending flotillas up or down stream.

But such a river has never proved a serious barrier against a vigorous and aggressive race, where it lies between two peoples, so that the aggressors have merely to cross it.

It offers no such shield as is afforded by a high mountain range.

The Mississippi served as a convenient line of demarkation between the Americans and the Spaniards; but it offered no protection whatever to the Spaniards against the Americans.
Importance of New Orleans.
Therefore the frontiersmen found nothing serious to bar their farther march westward; the diminutive Spanish garrisons in the little creole towns near the Missouri were far less capable of effective resistance than were most of the Indian tribes whom the Americans were brushing out of their path.