11 South LaSalle Street Building or Eleven South LaSalle Street Building (formerly Roanoke Building and Tower and originally Lumber Exchange Building and Tower Addition or simply the Roanoke Building and Lumber Exchange Building) is a Chicago Landmark building that is listed on the National Register of Historic Places and that is located at 11 South LaSalle Street in the Loop community area of Chicago, Illinois, United States. This address is located on the southeast corner of LaSalle and Madison Street in Cook County, Illinois across the Madison Street from the One North LaSalle Building. The building sits on a site of a former Roanoke building (once known as Major Block 2) that once served as a National Weather Service Weather Forecast official climate site and replaced Major Block 1 after the Great Chicago Fire. The current building has incorporated the frontage of other buildings east of the original site of Major Block 1.