The first of these Interstate conferences was held in January, 1898, at which the miners were conceded a further increase in wages. In addition, the agreement, which was to run for two years, established for Illinois the run-of-mine[53] system of payment, while the size of the screens of other states was regulated; and it also conceded the miners the check-off system[54] in every district, save that of Western Pennsylvania.[55] Such a comprehensive victory would not have been possible had it not been for the upward trend which coal prices had taken. But great as was the union's newly discovered power, it was spread most unevenly over the central competitive field. Its firmest grip was in Illinois. The well-filled treasury of the Illinois district has many times been called upon for large contributions or loans, to enable the union to establish itself in some other field. The weakest hold of the United Mine Workers has been in West Virginia. At the end of the general strike of 1897, the West Virginia membership was only about 4000. Moreover, a further spread of the organization met with unusual obstacles. A large percentage of the miners of West Virginia are Negroes or white mountaineers. These have proven more difficult to organize than recent Southern and Eastern European immigrants, who formed the majority in the other districts. And yet West Virginia as a growing mining state soon assumed a high strategic importance. A lower wage scale, the better quality of its coal, and a comparative freedom from strikes have made West Virginia a formidable competitor of the other districts in the central competitive field. Consequently West Virginia operators have been able to operate their mines more days during the year than elsewhere; and despite the lower rates per ton, the West Virginia miners have earned but little less annually than union miners in other States. But above all the United Mine Workers have been handicapped in West Virginia as nowhere else by court interference in strikes and in campaigns of organization. In 1907 a temporary injunction was granted at the behest of the Hitchman Coal and Coke Company, a West Virginia concern, restraining union organizers from attempting to organize employes who signed agreements not to join the United Mine Workers while in the employ of the company. The injunction was made permanent in 1913. The decree of the District Court was reversed by the Circuit Court of Appeals in 1914, but was sustained by the United States Supreme Court in March 1917.[56] Recently the United States Steel Corporation became a dominant factor in West Virginia through its ownership of mines and lent additional strength to the already strong anti-union determination of the employers.