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 >
Eli Whitney. a Yale graduate working in Georgia as a private tutor that invented the cotton gin (a simple device that consisted of rollers and brushes that separated the seed form the cotton very quickly, allowing for the growing/selling of cotton on a larger scale).