@metrodetroitnews: An estimated 40,000 people filled the streets of Dearborn on Saturday for the Arbaeen of Ashura march, the largest of its kind in the United States. The annual procession honors Imam Hussein, the grandson of the Prophet Muhammad, who was killed in the Battle of Karbala more than 1,300 years ago. For Shia Muslims, the march symbolizes standing against injustice and remembering Hussein's sacrifice. Dearborn police directed traffic and closed northbound Greenfield Road from Warren to Ford Road for several hours to accommodate the massive crowds. Officials say this year's turnout reached about 40,000, making it the largest Arbaeen gathering in the country.