An engraving depicting the York Street Flax Mill, Belfast An engraving depicting the York Street Flax Mill, Belfast. Founded by Mulholland in 1830 when the population of Belfast was approximately 50,000: by 1866 the population was 150,000. Dated 19th century Editorial use only. All other uses to be cleared with the copyright owner (World History Archive), in advance., WHA_136_0702.jpg, York Street Flax Mill; Belfast; Mulholland; 1830; population; 50,000; 1866; 150,000; engraving; 19th century; industrial revolution; textile industry; historical building; architecture; Northern Ireland; urban development; industrialization; cityscape; urban growth; historical landmark; industrial heritage; Irish history; manufacturing;