If your students are going to try to study American popular music, they need to know where it all came from.  Obviously, The blues are where to start.  Even a cursory understanding will help them to understand what American music means.

Blues

The Blues are one of the original genres of American music, and by far the most influential. Spawned from almost entirely poor, black musicians who lived along the Mississippi Delta during the Southern Reconstruction, the Blues came from old songs discussing how difficult life was in that area in that time. The Blues eventually found their way into Southern churches, helping to create Gospel music. Blues musicians worked with highly trained classical musicians from New Orleans as well as ragtime players from the Midwest, and as a result, Jazz was born. Blues guitarists helped to create rock'n'roll, with rock guitarists using Blues-based riffs for more than 70 years. Blues songs are still played and recorded, although less commercially viable than most of the genres they spawned, and the original form of The Blues has largely been unchanged.

Stylistic Traits: 12-bar blues harmonic structure, slower tempos, often in triple meter or swung rhythms, characteristic guitar timbre, as the guitar is the star of the Blues.

Instrumentation: electric guitar, bass, drumset, piano. Sometimes a horn section will accompany.

Lyrical Consideration: Blues songs are often lacking in profanity, although sometimes they may contain double entredre sexual references or references to alcohol.  As has become a standard idiom in American English, "singing the blues" refers to sorrow and expressing feelings about pain.

Examples:

Sister Rosetta Tharpe - "Didn't It Rain"

John Lee Hooker - "Serves Me Right to Suffer"

Ray Charles - "Georgia on My Mind"

B.B. King - "The Thrill Is Gone"

Gary Clark Jr.