What's the Kennection? #61

What venue at 511 10th Street Northwest in Washington, D.C., contains a museum displaying a derringer and a blood-stained pillow?

Nina Wilcox Putnam, who created Boris Karloff's character "the Mummy," also designed what IRS document, the individual income tax return?

A Simpsons character is named for what famed behavioral psychologist who wrote Walden Two?

A tiny seven-by-eight-foot shed in Ochopee, Florida, is the smallest of what kind of facility in the United States?

What was the most popular Internet music streaming service for a full decade, until Spotify dethroned it last year?

What's the "Kennection"?