József Kossalkó was born on January 5, 1832, in Nagysáros, and was ordained a priest on July 27, 1855. He began his priestly career in the Diocese of Szepes, and in 1858 he was transferred to the Diocese of Košice. During his service in Hungary, he served as an assistant pastor in Szepesváralja, Béla, Klukno, and Nagysáros; later, he was a chaplain with the 66th Infantry Regiment, and subsequently served as a pastor in Bátya, Lapispatak, and Ossikó.

In 1884, he emigrated to the United States, where he first appeared in Streator, Illinois, and later became the pastor of the Slovak Catholic community in Hazleton, Pennsylvania. According to the history of St. Joseph Parish in Hazleton, he served as the parish’s second pastor from April 8, 1890, to February 28, 1892. During his tenure, the parish went through a difficult period, and after his departure, it remained without a permanent pastor for a long time. The parish’s official history clearly states that he returned to Europe in 1892.

According to surviving Hungarian and American records, his work in the United States was not without problems. In Hazleton, a serious conflict arose between him and some of the parishioners, and according to Hungarian sources, he was even accused of embezzlement, though the details of this have not yet been verified from primary archival sources. The later period of his life is particularly uncertain. According to other sources, he served in Bridgeport, Pennsylvania, between 1893 and 1910; however, this is difficult to reconcile with the Hazleton parish’s statement that he returned to Europe in 1892.

The place and date of his death remain unknown. Based on the available data, it can be established with certainty that he was among the American Slovak Catholic pastors of the late 19th century; however, his ministry is overshadowed by conflicts and circumstances that remain unclear to this day.