I believe the answer would be cotton gin because the invention of the cotton gin was able to become more efficient in harvesting cotton.
During the American Civil war, the Confederacy hoped to receive assistance from France and Great Britain because they sold cotton to them.
Well, the chinese big secret was silk. So that would be my best guess.
You seem to be giving a statement more than asking a question, but the period you describe ran from about 1815 to 1825, and is most closely associated with the presidency of James Monroe.
The phrase "Era of Good Feelings" was coined by a journalist, Benjamin Russell, in the Boston newspaper, <em>Columbian Centinel</em>, on July 12, 1817. Russell used that term to describe the new era taking shape, especially as Monroe's presidency began, after Monroe visited Boston as part of a goodwill tour of the US. President Monroe certainly went along with the description and was trying to evoke that "good feelings" sort of mood in the country. Historians see "The Era of Good Feelilngs" as having begun around 1815, after the War of 1812 and the end of Napoleon's wars in Europe, when the United States entered an era when it could focus on its own affairs and not need to be concerned about political and military happenings in Europe. The "Era of Good Feelings" is strongly associated with Monroe's two-term presidency, from 1817 to 1825. President Monroe made goodwill tours of the country in 1817 and 1819 to promote national pride and national unity.
