well, there's kind of a blur as to what's classified as concept work, fantasy work etc. you could argue that almost any painter who painted scenes did concept art.
giovanni battista piranesi did an amazing massive series of etchings of an imaginery infinite prison. really amazing and worth checking out here...go to carceri d'invenzione. or google them.
got lot of views here. the history may extend to the cave art. but in terms of technology or when was it applied first in to motion or animation or film industry. very tru tht every artists impression is a concept art but in todays term it has become a professional terminology.
animators from walt disneys studio practiced concept art. logically... animation industry was the first industry to apply this term and then it was adapted in films. star wars is aa recent film in which it was used.