On this day in US history, Zebulon Pike, the army officer who led an exploring party in 1805 to find the source of the Mississippi River, set off on a new expedition to explore the American Southwest on July 15, 1806. Pike was instructed to find the headwaters of the Red and Arkansas rivers as well as to investigate Spanish settlements in New Mexico. The information provided by his expedition provided great impetus for future US settlement; his reports about the weakness of the authority the Spanish held over parts of the territories stirred the talk of US annexation.
