I have been hearing a lot about Seattle in the news lately, but I don't know much about the city.  Is Seattle the capital of Washington state?  
No I believe Olympia is Washington's capital. Seattle is however the largest city in the state of Washington. 
What is the population of Seattle?  I assume several million.
Estimated 713,700 residents. That also makes it the largest city in the Pacific Northwest region of North America.
That's amazing.  Is there anything significant either historically or practically about Seattle?
Seattle has been one of the fastest growing cities in the U.S. It must be great there, since everyone is flocking to it.
Do you know about any significant businesses there?  I know they have a professional football team that blew it in the Super Bowl against the Patriots.
Seattle
Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With an estimated 744,955 residents , Seattle is the largest city in both the state of Washington and the Pacific Northwest region of North America. According to U.S. Census data released in 2018, the Seattle metropolitan area's population stands at 3.94 million, and ranks as the 15th largest in the United States. In July 2013, it was the fastest-growing major city in the United
in the state with a population of over 100,000 (Seattle, Spokane, Tacoma, Vancouver, Bellevue, and Everett) as well as the state capital, Olympia.
Interstate 90 (I-90) is the longest primary Interstate Highway in Washington, which connects Seattle to Spokane and the Idaho border, measuring , while I-82, connecting the Oregon border city of Umatilla to Elensburg via Yakima, is the shortest at . The longest auxiliary Interstate Highway in Washington is I-405, a bypass of Seattle through the Eastside, at , and