I want to know the answer to the following question:
who declated the American frontier "closed" in 1893?
All the background I'm provided with is that "Several hundred thousand square miles (several hundred thousand square kilometers) of the Great Plains have fewer than 6 inhabitants per square mile (2.3 inhabitants per square kilometer)—the density standard Frederick Jackson Turner used to declare the American frontier "closed" in 1893.". Is that enough to answer the question?
Answer: yes