The Poznań and Lwów gasworks were established in the 1850s; the former being an urban enterprise, the latter a private company. At the beginning of the 20th century, the gasworks and the entire gas infrastructure in Lwów were seriously outdated as compared to Poznań in terms of the volume of production and technology. After the municipalization of the plant in 1898, Galicia’s capital quickly began to reduce a backlog using the effects of technical progress in Europe. As part of the modernization and expansion of both gasworks in the fi rst decade of the 20th century, modern water-gas plants with Humphreys & Glasgow systems were commissioned in Poznań (1900) and Lwów (1906). Moreover, the gas network and public lighting system were intensively developed in both cities. In 1910, 11.3 million cubic meters of gas fl owed into the municipal network in Poznań, whereas 6.1 million cubic meters did so in Lwów. The number of gas street lights amounted to 3456 and 3541, respectively. In both cities, major extensions of their gasworks were planned in the very years preceding the outbreak of World War I. In Poznań, the investment was implemented to a large extent during World War I, when a unique and innovative Koppers retort house and a dry-seal gas holder with a capacity of 50 thousand cubic meters were built. In Lwów, due to the Russian occupation of the city between 1914 and 1915, ultimately the works had to be stopped. Due to wartime hardships, the planned Glover-West vertical retort house was eventually replaced by the Dessau vertical retort furnace. The retort house was completed in 1917, but the rest of the investment was fi nalized in the fi rst years of the Second Polish Republic. Nevertheless, when the Partitions of Poland ended, both gas plants were among the largest and most modern in terms of technology in the country, in which their directors at the time, Hans Mertens in Poznań and Adam Teodorowicz in Lwów, had considerable merit.