Nikolaus Gross grew up in the Ruhr valley in a blacksmith's family. After leaving elementary school, his first job was in a steel mill. From 1915 on, he worked in a mine. In 1917 he joined the Gewerksverein christlicher Bergarbeiter (Trade Organization of Christian Miners) and served as labor union secretary in Oberhausen, Silesia, and Saxony before returning to Bottrop in 1924. From 1926 on, he belonged to the close circle of associates of Otto Müller, president of the Verband Katholischer Arbeiter- und Knappenvereine Westdeutschlands (Association of Catholic Workers' and Miners' Organizations of Western Germany). In 1927 Gross became editor of the newspaper Westdeutsche Arbeiterzeitung and worked in close cooperation with Bernhard Letterhaus. Both of them were openly critical of the National Socialists even before 1933. When the Westdeutsche Arbeiterzeitung was banned in 1938, Gross published its successor, the periodical Ketteler-Wacht. From 1941 on, he provided spiritual guidance for men and sought to use this channel to continue the work of the association. Gross was repeatedly arrested and interrogated. His association with Carl Goerdeler and Jakob Kaiser came to light after July 20, 1944. On August 12, 1944, he was arrested, and he was sentenced to death by the People's Court on January 15, 1945. Against all regulations, his wife Elisabeth was allowed to see him one last time in Berlin's Tegel prison. Nikolaus Gross was murdered a short time later in Berlin-Plötzensee.