Congressman Jesus "Chuy" Garcia and Congresswoman Jan Schakowsky met with workers and union leaders at the store on North California Avenue Saturday afternoon.
Workers at the Starbucks on North Wabash announced at the start of the year that they were going to vote to unionize.
"It really is a movement and to see these workers standing up across the country, it gives hope to all of us that we really are able to improve workers lives, when workers understand that they have power," one supporter said.
If this passes the Loop Starbucks will be the first Midwest coffee chain shop to unionize.
Almost one month ago, a Starbucks in Buffalo, New York became the first group of Starbucks workers to unionize across the country.