<Tr> <Th> Designated </Th> <Td> April 19, 1999 </Td> </Tr> <Tr> <Th_colspan="2"> References </Th> </Tr> <P> The Space Needle is an observation tower in Seattle, Washington, a landmark of the Pacific Northwest, and an icon of Seattle . It was built in the Seattle Center for the 1962 World's Fair, which drew over 2.3 million visitors, when nearly 20,000 people a day used its elevators . </P> <P> Once the tallest structure west of the Mississippi River, it is 605 ft (184 m) high, 138 ft (42 m) wide, and weighs 9,550 short tons (8,660 tonnes). It is built to withstand winds of up to 200 miles per hour (89 m / s; 320 km / h) and earthquakes of up to 9.1 magnitude, as strong as the 1700 Cascadia earthquake . It also has 25 lightning rods . </P>

What's the purpose of the space needle