The Blues was born in the Mississippi Delta. It emphasized the guitar and harmonica instead of trumpets and a banjo that New Orleans Jazz had popularized.
It is a deceptively simple musical structure. Only six notes in a scale (a 'normal' scale has seven notes) and usually just three chords (the first, fourth and fifth chords in the key, for those keeping score). But from that simple formula comes a huge amount of popular music from the past 50 years. Everything from Chuck Berry to Elvis's Don't Be Cruel to the Monkees to Led Zeppelin are just variations on the style pioneered by sons of sharecroppers from Mississippi.
Robert Johnson is the guy who was said to have sold his soul to the devil to learn how to play guitar.
The Rolling Stones started out as a blues cover band. The story goes that when they were booking their first gig, the bar owner was on the phone and asked Brian Jones what their band was called. Jones saw this song title on the back of an album lying on the apartment floor.
The harmonica is an integral part of many blues songs. Sonny Boy Williamson was one of the best.
After WW II, many blues players moved to northern cities, especially Chicago. Chicago Blues is usually electric and often adds a horn section. There are still bars in Chicago where you can hear live blues, such as Blue Chicago (bluechicago dot com) on La Salle Drive on the north side.
Otis Rush is one of my favorites of the Chicago style.
Another classic Chicago blues player. This guy died way too young but the two albums he made are both fantastic.
I'll admit that Howlin Wolf's voice is an acquired taste.
One of my proudest moments as a father was when this song came on the car stereo and my daughter turned it up.
T-bone Walker used to play his guitar behind his back or with his teeth. Some guy named Hendrix thought that looked pretty cool.
Those metal bars on the neck of a guitar are frets. Pressing the string down against a fret makes a specific note. You are changing the length of the vibrating string, which changes its tone. But if you don't press the strings against the fret and instead change the length by holding something on the strings themselves, you can get one note to 'slide' into another note.
When Duane Allman is the one holding the slide, you get this (the song starts at 0:54):
And finally there is Stevie Ray Vaughan. The thing that sets him apart from guys like Clapton in my mind is that he could play rhythm as well as lead, and his leads could go effortlessly from blistering to mournful and back again. IMO, he outplays Albert King here.