The IWW was founded by anarchists and socialists who believed labour unions like the American Federation of Labor were not doing a good job with uniting workers. The IWW's goal was to promote worker solidarity and overthrow the ruling class. The IWW criticized the AFL for not going far enough to secure workers, a slim percent of American workers belonged to unions in 1905. The IWW supported the concept of a general strike, in which all of the workers of a county or area would strike forcing the government to give into the workers' demands and planting the seeds of revolution against capitalism.
The IWW gained support quickly, unlike other unions, the IWW allowed women, African Americans, Asians, and all immigrants to join. The press and politicians condemned the IWW for being against Free Market policies and too radical. They would try to disrupt IWW meetings non-violently and violently; many IWW members were arrested for no reason. Some members were even killed. If anything, all of these attacks only encouraged membership to the IWW.
The IWW participated in strikes early on. The IWW supported free speech and fought for it, even if it meant many members being arrested. By 1925, the IWW had 25,000 members and was involved in over 150 strikes. It was difficult to maintain membership. After strikes, companies forced workers out of the IWW with threats and promises.
Most IWW members were against World War I, they believed it was a ploy to make workers fight against workers while the capitalist pigs gained more money. In 1917, the IWW announced it had declared war on capitalist America. American politicians turned the population against the IWW with propaganda and restrictions of freedom of speech. Over 170 IWW leaders were arrested for "conspiring to hinder the draft." The Espionage Act of 1917 basically ruled that it was a-okay to restrict freedom of the speech during a war.
Near 1930, the IWW was on its last legs, suffering from the Palmer Raids which deported foreign-born members and the group was suffering from internal issues. By 1930, membership was at 10,000. Membership continued to dwindle until the 1960s.
The Civil Rights movement helped membership go up, but not as much as when the IWW was first formed. The IWW only participated in minor strikes. Since then, the IWW has been a part of many strikes but membership is very low and only at about 5,000.
Being a communist ideology, the government naturally hated the IWW and tried many times to destroy the IWW. In 1916, the police attacked and killed five IWW members on the steamboat Verona. Many members were arrested for not supporting World War I and all of them were arrested.
The Espionage Act of 1917 ruled that freedom of speech could be restricted during times of war. So the government took advantage of this and arrested many IWW members and former members. Some were lynched in jail. Seventeen members were tarred and feathered by the KKK at an incident known as the Tulsa Outrage.
During the Palmer Raids, many immigrant members were deported.
The Second Red Scare made Americans once again hate anything that resembled communist and membership hit an all time low. The U.S. government labled the IWW as communist and said that it was involved with Comintern.