Explain ONE historical situation in the period 1750–1900 in which individuals freely chose to migrate.

THE FOCUS OF THIS ERA IS EUROPE/WEST.  EUROPE's DOMINATION WAS ONLY ASSURED BY THE END OF THE PERIOD, 1900.  IN 1750, CHINA IS THE WORLD'S BIGGEST MANUFACTURER. CHINA WILL REMAIN THE LARGEST MANUFACTURER UNTIL THE 1830s AND WASN'T SURPASSED BY THE US UNTIL THE 1880s. SO, DON'T SKIP PAST CHINA, JAPAN, the OTTOMANS, LATIN AMERICA, and AFRICA)

Explanation:

The previous era was dominated by European discovery.  This era is dominated by how these Europeans handled their new-found success both ECONOMICALLY (Industrial Revolution) & POLITICALLY (Revolutions).  Much like the Mongols and Muslims of the Post Classical, this era is essentially the Industrial Revolution & the Enlightenment-driven Revolutions (French, US, Latin America, etc.).  One could argue that the Industrial Revolution is the most important thing that ever happened.  Besides the Columbian Exchange, its the only other thing I can guarantee that will be on the AP test.  This is also the only era with 4 subsections: Industrial Revolution, Imperialism, Revolution, and Migration. This is the Modern Era...

these civilizations were located around fertile rivers, where they could produce an abundance of crops