From one of my favorite blogs, The Presurfer:
Close to Buescher State Park near Smithville in Texas you can find the world's largest text. By clearing forest so that a pattern would be visible to landing aircraft, a landowner outside Austin, Texas created a target that is also useful for evaluating spatial resolution of astronaut photographs.
The forest was selectively cleared in order to spell the landowner's name 'LUECKE' with the remaining trees. According to local surveyors who planned the clearing, the plan was to create a word that was 3100 by 1700 ft long.
Links: Google Sightseeing - via The Presurfer
What a waste of trees...
--TwoDragons
I just found the spot on Google Earth (it's pretty easy to find, once you've got Smithville in view) and measured it; it is indeed 13,720 feet long and 3,100 feet high. Guess they really do do things big in Texas.