Born Dec. 14, 1841, in Roskilde, Denmark; died July 8, 1894, in Chicago, USA. Danish labor leader.
A former lieutenant in the Danish Army who was stirred by the Paris Commune of 1871, Pio became one of the first propagandists of socialism in Denmark. He helped organize the Danish section of the First International and the Social Democratic Party, which grew out of the Danish section in 1871. He was also a founder (1871) and editor (1871-72) of the workers’ newspaper Socialisten. Imprisoned from 1872 to 1875, Pio in 1876 directed the reestablishment of the Social Democratic Party, which had been abolished by the authorities in 1872. In May 1876 he visited K. Marx in London. He corresponded with F. Engels. In his political views, Pio was a follower of Lassalle. In 1877, Pio emigrated to the USA, where he continued his socialist propaganda.