The U Drop Inn portion of the famous Shamrock, Texas Conoco Station, on Route 66
restored in recent years, and now is a museum.
Some links: http://texasescapes.com/TexasGasStations/Shamrock-Texas-Tower-Conoco-Gas-Station-1935.htm
More: http://www.oldgas.com/info/towerconoco.html
More: http://www.roadsideamerica.com/tip/17371
More: http://www.takemytrip.com/08plains/08_50a.htm