Their’s was the lot - i. e. “the first lot.” The Kohathites had the first lot among the Levitical families, as being the family whereto the high priesthood was attached (compare Joshua 21:10).
Related Commentaries of 1 Chronicles 6:54
1 Chronicles 6:54
54 Now these are their dwelling places throughout their castles in their coasts, of the sons of Aaron, of the families of the Kohathites: for theirs was the lot.