Friday marked the 30th anniversary that Washington was elected to office, becoming the city's first African-American mayor.
He died in November of 1987, shortly after winning his second term.
Earlier Friday at a news conference announcing the tribute, Illinois lawmakers released statements calling Washington a pioneer.
"Governor Pat Quinn on reflecting on Harold Washington said, 'Harold Washington will be remembered as a giant in the history of America's big city mayors,'" said Debrah Prabal. "Not content to be a trail blazer, he was transformational; profoundly changing the way Chicago governs itself."
The city council has declared April 15th Harold Washington day in the city.
Also going on at this hour is a commemorative reception at the Marmom Grand Hotel.
A closing celebration will be held April 29.