Filling cells

Dumb question...I have a 15K row worksheet that was imported from a syndicated sales database. It is auto laid out by retailer name in the first cell of column a, then in column b are all the items of a given brand sold in that retailer. (see attached portion of database for what I mean). I want to pivot table this data so I want the empty cells in Column A populated with the Retailer name at the beginning of each "chunk" without having to drag and drop to fill. What is the best way to do this? Thank you for your assistance!