The comment about chord progressions missed the point: it was common before 1920 for white blues musicians to learn songs, stanzas, melodies from black blues musicians. Sam McGee recalled that he was in about 1910, e.g. Very often we have no recordings of the same songs by black blues musicians. So even if you're only interested in black musicians (which is not true of me), we can learn a lot about early black blues from people like John Carson.

Here are some of the recordings of interest:

Bert Bilbro "Mohana Blues"
Samantha Bumgarner "The Worried Blues"
Dick Burnett "Curley-Headed Woman"
John Carson "Tom Watson Special," "Goin' Where The Climate Suits My Clothes"
Warner Carver "Sisco Harmonica Blues"
Cleve Chaffin "C & O Whistle" by the Fruit Jar Guzzlers
Tom Darby "Heavy Hearted Blues," "Goin' Down That Lonesome Frisco Line"
Van Edwards "Yodeling Blues" by the Buck Mt. Band
Ollie Gilbert "Good Mornin' Blues"
Banmon Grayson "Going Down The Lee Highway"
Roy Harvey "Steamboat Man," "Railroad Blues"
John Hatcher "Tishomingo County Blues"
Louise Henson "I'm A Stranger Here"
Molly Jackson "I Got Up This Morning, Put My Clothes On Wrong"
Earl Johnson "Wire Grass Drag"
Jimmy Long "Doggone Blues"
Bascom Lunsford "Hesitation Blues"
Dave Macon "Hill Billie Blues," "I've Got The Mourning Blues"
Palmer McAbee "Lost Boy Blues"
Sam McGee "Railroad Blues"
David Miller "Way Down In Jail On My Knees," "Jailhouse Rag"
Sam Moore "Chain Gang Blues"
Willie Narmour "Carroll County Blues"
Tex Owens "Train Whistle Blues"
Charlie Poole "If The River Was Whiskey"
Riley Puckett "K.C. Railroad"
Ike Reaves "Hesitation Blues"
Posey Rorer “The Cat's Got The Measles And The Dog's Got The Whooping Cough” by Walter Smith
Manco Sneed "Florida Blues"
Pete Steele "The Weary Blues," "Payday At Coal Creek"
Bunt Stephens "Louisburg Blues," "Left In The Dark Blues"
Cleve Sutphin "Lonesome Road Blues"
Jimmie Tarlton "Way Down In Florida On A Hog," "Put-Together Blues"
Ben Tinnon "Plow Boy Hop" by the Grinnel Giggers
Marion Underwood "All Night Long" by Byrd Moore
George Walburn "Dixie Flyer"
Wade Ward "Chilly Winds"
Henry Whitter "Lonesome Road Blues"
Jess Young "The Old K-C"