Thousands of people chanted, picketed and marched on cities across America as May Day demonstrations raged against President Donald Trump’s immigration policies. Police in Oakland, California, arrested at least four activists who chained themselves together to block a county building. More than 100 other activists there demanded an end to what they called a collaboration between county law enforcement and federal immigration agents. Despite the California clash, the initial rounds of nationwide protests were largely peaceful as immigrants, union members and their allies staged a series of strikes, boycotts and marches to draw attention to the importance of immigrants in the United States. The demonstrations on May Day, celebrated as International Workers’ Day, follow similar actions worldwide in which protesters from the Philippines to Paris demanded better working conditions.