From the American Heritage Dictionary website:
In contemporary English, here refers to the speaker’s location regardless of whether the sentence involves things or people remaining in that place, moving to that place, or leaving that place. We say I have been waiting here for hours or Come here! or Get out of here! But historically English has used three separate adverbs to convey these three different relations to place. A speaker of the sixteenth century might have said I have been waiting here for hours, but she would have said Come hither! instead of Come here! and Get thee hence! instead of Get out of here!
Likewise, when referring to a location other than where we are, we now use there indiscriminately: Who is there? I will take you there. We sailed from Ireland to Iceland and from there to Greenland. Our sixteenth-century speaker, for her part, might have said Who is there? but I will take you thither or We sailed from Ireland to Iceland and thence to Greenland.
Finally, for asking about places, though English relies now on just where, there were once three separate adverbs. If our twenty-first-century speaker says Where am I? or Where are you going? or Where is that smell coming from? our hypothetical Elizabethan speaker might say Where am I? or Whither goest thou? or Whence cometh that reek?
More here. [Thanks to Steven Pinker.]