Misc: In 1834 Pres ---------- orders 1st use of US troops to suppress a labor dispute.?

Questions

The only river that flows both north and south of the equator is the -------------. It crosses the equator twice.?

The only three countries in the world whose names begin with "Z" are Zambia, Ziare and ----------, all in Africa.?

Reykjavik, --------------- is likely the cleanest capital city in the world.?

The Oregon Trail (1840-1860), the route used during the westward migrations of the United States, started in ------------- and ended in Oregon and was about 2,000 miles long.?

Ruby Falls, America's highest underground waterfall open to the public, is located on historic Lookout Mountain in Chattanooga, ---------------?