You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "when did unions start in the united states?" whose answer is mid-19th century.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when did unions start in the united states
Useful Output:

Doc 1: The first union in the USA was formed in 1794. It consisted of the shoe-makers who worked for Carpenter's Company in Philadelphia. They were
Doc 2: The first national federation of unions, the National Labor Union, was created in 1872 after workers demanded for an eight-hour workday.
Doc 3: They formed a number of union federations after the Civil War, including the National Labor Union in 1866, the Knights of Labor in 1869, and the
Doc 4: Unions in Philadelphia joined together to create the first trade association in 1827. After the publication of an anonymous letter titled “To
Doc 5: The National Labor Union was founded in Baltimore, Maryland, on August 20, 1866. It was created to mandate an eight-hour workday for federal