The period outside the quotation marks is not a copy error. For at least two centuries, it has been standard practice in the United States to place commas and periods inside of quotation marks.
A: The cotton gin was invented by Eli Whitney in 1794. It revolutionized the cotton industry in the United States but became a controversial invention as it b... Full Answer >
The cotton gin was not Eli Whitney's only contribution to the Industrial Revolution in America. He also started the first factory which used interchangable parts in manufacturing. With a growing free black population in northern and border states, 95 percent of the country's African American population was enslaved in 1820.