How did William Clark die?

After the expedition, Clark would serve as governor of the Missouri Territory (from 1813-1820) and he continued to lead Native American affairs for 30 years, enjoying a high reputation as an authority on the West. Many hunters, adventurers and explorers would visit him in St. Louis for advice. He died at age 69, on September 1, 1838, while at the home of his son, Meriwether Lewis Clark. His cause of death is unknown and is only described as a "brief illness."