The First Klan was a thoroughly Southern phenomenon, formed in the wake of the Civil War, it was a terrorist organization which visited violence upon newly freed African-Americans, northern carpetbaggers who had come south during Reconstruction, and local scalawags who were seen as too complicit in the perceived occupation the states which had recently been engaged in insurrection.

The Second Klan, founded in 1915, originated in the South as well, but became a thoroughly national phenomenon. Some of the post powerful Klan organizations existed outside of the South in that period, such as Indiana which was considered a Klan hotbed of the period. This older answer looks at the Midwest, this one touches on New England, and this one the Pacific Northwest.

As you specifically noted you are mainly looking for resources, I would point you towards Richard's Not a Catholic Nation: The Ku Klux Klan Confronts New England in the 1920s, Baker's Gospel According to the Klan: The KKK's Appeal to Protestant America, 1915-1930, Jenkins's Steel Valley Klan: The Ku Klux Klan in Ohio's Mahoning Valley, and Moore's Citizen Klansmen: The Ku Klux Klan in Indiana, 1921-1928.