In the news: Ku Klux Klan resurgence in 1920s

Report probes history of KKK at UW-Madison; $1M history exhibit planned.  (Wisconsin State Journal,  4/19/2018)

Link to full report

Source:  Ku Klux Klan Facts and Summary (History.com, emphasis added)

U.S. population in 1920:  106,021,537.  
Meaning that, as far as a percentage of the total US population is concerned, an equivalent membership today would be 12,300,000.

UW students check off 2 grievances on their intolerance list:  Roman Catholics and foreigners.

From the above-cited State Journal article.  However, there is evidence some members of the first group participated in what the report describes as an “extra-legal ... campaign against liquor sellers in (Madison’s) Greenbush neighborhood” in 1921, when Prohibition was in effect. The members, circumventing local police, staked out the neighborhood and summoned federal liquor control officers there, resulting in the arrest of eight Italian-American liquor merchants.

Related reading:
The Ku Klux Klans Surprising History.  (The New York Times Book Review, 12/4/2017)
The KKK and UD in the 1920s.  (University of Dayton, 9/8/2017)
A College and Klan Tradition (Wesleyan College, Georgia).  (Inside High Ed, 6/23/2017
Ku Klux U: How the Klan almost bought a university. (Hoosier State Chronicles. 1/6/2016)
The Ku Klux Klan in Calvin Coolidge's America.  (Calvin Coolidge Presidential  Foundation, 7/14/2014)
78 years ago:   Notre Dame battles the KKK.  (The Irish Echo, 2/16/2011)
Kampus Klan:The University of Nebraska-Lincoln and the Ku Klux Klan, in the Early 1920s.  (Nebraska U, Spring 2008)
Ku Klux Klan at the University of Illinois FAQ.  (2004)
The Ku Klux Klan at Harvard.  (The Crimson, 2/18/1999)