What happens in the US during the period of 1835-1842 according to the book?

In 1836-37 a cholera and smallpox epidemic spreads through Edenton. Harriet becomes desperately ill and nearly dies but for the medical support of her brother John. Gran also becomes ill, but eventually recovers. In late 1837, Mr. Sawyer is elected to the United States Congress and goes to Washington, D.C.