Although the Illinois National Guardsmen stationed at the Chicago Avenue Armory were busy between the First World War and 1968 (the 122nd Field Artillery was active in WWII and the 106th Cavalry was also mechanized for WWII service - see the 106th's entire history, here), riots following the assassination of Martin Luther King Jr. and during the Democratic National Convention brought the Guardsmen and the armory site into prominent focus.

In my recorded conversation with Michael Butler, he tells me of a meeting with members of the Yippie group who would become known as the Chicago Seven, and who were charged with inciting the riots during the Chicago Democratic Convention. Butler was the producer of the original production of Hair, which opened on Broadway at the end of April 1968, within weeks of the Martin Luther King assassination. When Butler inquired about where the proceeds were going from a Yippie benefit performance, he was told that the money would be used for martial arts instruction to "go after the pigs."

Hear Michael Butler's account, here:

Chicago Tribune headlines, April 6-7, 1968, after Martin Luther King Jr. was killed in Memphis on April 4.

In an editorial response to a photograph of protesters at the Chicago Avenue Armory, on April 10 1968, a Tribune editor wrote:
The demonstrators, some of them long-haired hippies, were members of something called the National Mobilization Committee to End the War.
Several of them were arrested by Chicago police.
It is easy to wax indignant over a bunch of clowns who try to disrupt operations of the guard in endeavoring to return peace to the streets in one of the city's most serious emergencies. These people know that President Johnson's bombing pause above the 20th parallel in Viet Nam has been productive of offers from Hanoi to engage in preliminary and conditional talks. The demonstrators must be working for communist North Viet Nam.
It is an outrage that this country has to deal with a second front at home against rioters and beatniks when its fighting men are risking death overseas.

Chicago Tribune headlines during the August 1968 Democratic National Convention.