This paper deals with the activities performed and steps taken to increase production activities in Zonguldak-Ereğli Coal Field between 1920 and 1960 and the contributions of coal production attained as a result of these activities and steps to the economy of Turkey. This study presents all kinds of activities carried out to increase production in the field as well as relevant modernization works from 1836, when the first production was made, until 1960. The developments in the above-mentioned period were examined in four sections: coal enterprises during the Ottoman period between 1836 and 1920 (to provide a background for the period under examination); the developments in the 1920-1923 National Government period; the developments in the 1923-1940 Republican period; and the developments in the 1940-1960 involving nationalization of the field and the aftermath. The contributions of developments that took place in coal production during these periods to national economy are presented in the form of numeric data. The gaps in the literature regarding the topic of this study were eliminated by using primary sources. Relevant evaluations were made by taking into account Turkey in that period and the developments that took place in the field of hard coal in the world. The results are as follows: legislative regulations that were made from 1920 in relation to the field yielded their fruits as of 1924 when production increased. However, private enterprises did not use the field rationally. Therefore, the expected level of coal production was never achieved. Before the nationalization of the field, the government established institutions such as General Directorate of Mineral Research and Exploration and Etibank and Ereğli Coal Enterprise. Later on, another governmental institution, Turkish Coal Enterprise, was founded and put into operation. In addition to all these institutions, foreign aids were received through the Marshall Plan, which led to a gradual increase in the production each year. Thanks to this increase, coal mine made important contributions to the economy through its use in transportation sector, heating official institutions and houses, producing electrical energy and coal gas, developing the iron, steel, and chemical industry, and supporting foreign currency inflow through export