CHICAGO (CBS) — The annual Car Wash Show will once again take up residence at McCormick Place starting in 2014.

The Car Wash Show, which has been held in Las Vegas for several years, is the world’s largest car wash convention and trade show, and one of the 200 largest exhibitions in the country. About 6,000 conventioneers from 30 countries attend the event, which includes 125,000 square feet of exhibits, and 20 hours of business seminars, according to the Mayor’s office.

“I am pleased that The Car Wash Show is coming to Chicago, and that it’s more than 6,000 attendees will have a chance to experience all the great things our City has to offer,” Mayor Rahm Emanuel said in a news release. “Attracting shows like this is a central focus of our comprehensive business and tourism strategy; they create jobs for our residents and foster economic opportunity throughout the city. We will continue to seek more exciting shows that will bring thousands of visitors to Chicago.”

The expo was last held in Chicago in 2002, and it had been held in Las Vegas for the past six years.

Just last year, the International Carwash Association elected not to bring its convention – then known as the Car Care World Expo to McCormick Place – due to uncertainty about work-rule reforms at the convention center.

Back in 2009, several conventions left McCormick Place, complaining about high union fees, and too many different unions, jurisdictions and work rules being involved in the setup process.

The resulting outrage resulted in the state-mandated overhaul. State lawmakers passed a bill that cut labor costs by allowing exhibitors to do their own setup, and also by letting them use outside electricians and bring in their own food, bypassing convention center unions. It doubled the ground transportation tax charged on trips to and from Chicago’s airports to boost tourism spending.

The overhaul survived a veto by Gov. Pat Quinn, and then-Mayor Richard M. Daley credited the changes for keeping McCormick Place alive.

a href=”http://chicago.cbslocal.com/2011/04/30/shows-will-flee-mccormick-place-over-work-rules/”>But last year, several unions have challenged the overhaul, and U.S. District Judge Ronald Guzman ruled in their favor and tossed the reforms.

However, Mayor Emanuel worked with McCormick Place officials, labor unions, and elected officials statewide to resolve the labor issues at McCormick Place, an act his office credits with bringing a number of trade groups to return or extend their conventions at the facility.