Songster Bob--If you feel that proximity to the South created the mindset that allowed the lynchings, tell me what you think about this incident, Duluth Lynching Homepage , which took place more than a decade before. Also check this, Omaha Courthouse Lynching which was witnessed by a young Henry Fonda--

By the time the Marion lynchings took place, lynchings, particularly Southern lynchings, had become a lot less common. Race riots, (or, more accurately, massive mob assaults on urban black communities) had become much more common, and they were a much more of a Northern phennomenon--they were worse than lynchings, insofar as that they involved not only murder and torture(and on a larger scale), they also involved massive destruction of homes and property.

The rioters were mostly laborers, often immigrants--the kind of folks we like to mythologize rather than revile.