When was the first air traffic control tower built?

What type of people build the great pyramids in Egypt? What is Stonehenge dedicated to? How is transportation important to a civilization? Why is there a nail in the Liberty Bell? What did it mean when Julius Caesar and his army crossed the Rubicon River? What is tropical rainforests named after? What is the floor of a river valley on either side of a river called? How many cm is burj kalifa? Is the Great Barrier Reef shrinking? When did the design for a concentric castle change? What river in Maine flows between the Katahdin Mountains and the Blue Mountains? What is the distance between jurusalem to sea of galilee? Why does it rain when it does? What is a famous bridge in England but not the London bridge? What river is the Delaware water gap a part of? Which Spanish missions were established throughout the Southwest and Texas? What coaster at cedar point top at 93 mph held the tallest record at 310 feet? What is the difference between getting your tooth pulled and getting a root canal? Was the great plains man made or natural feature? What is the name of the wonders of the worlds?

When was the first air traffic control tower built?