<P> The Progressive Era also brought reforms in working conditions for Maryland's labor force . In 1902 the state regulated conditions in mines; outlawed child laborers under the age of 12; mandated compulsory school attendance; and enacted the nation's first workers' compensation law . The workers' compensation law was overturned in the courts, but was redrafted and finally enacted in 1910 . </P> <P> The Great Baltimore Fire of 1904 burned over 30 hours, destroying 1,526 buildings and spanning 70 city blocks . More than 1,231 firefighters worked to bring the blaze under control . With the nation's entry into World War I in 1917, new military bases such as Camp Meade, the Aberdeen Proving Ground, and the Edgewood Arsenal were established . Existing facilities, including Fort McHenry, were greatly expanded . </P> <P> After Georgia congressman William D. Upshaw criticized Maryland openly in 1923 for not passing Prohibition laws, Baltimore Sun editor Hamilton Owens coined the "Free State" nickname for Maryland in that context, which was popularized by H.L. Mencken in a series of newspaper editorials . </P> <P> Maryland's urban and rural communities had different experiences during the Great Depression . The "Bonus Army" marched through the state in 1932 on its way to Washington, D.C. Maryland instituted its first ever income tax in 1937 to generate revenue for schools and welfare . Baltimore was a major war production center during World War II . The biggest operations were Bethlehem Steel's Fairfield Yard, which built Liberty ships; and Glenn Martin, an aircraft manufacturer . </P>

Why do they call maryland the free state
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