The creation and use of an intelligent transportation systems archived data user services data mine that is available on the World Wide Web are described. The transportation infrastructure in the Seattle metropolitan area is instrumented with thousands of inductance loops. The data from these loops can be used in a variety of modeling and transportation planning activities. However, only with a large repository of this data, covering a significant geographical area and a long temporal period, can complex research and planning questions be posed and answered. Such a repository or data mine is described in terms of the steps necessary to create such a repository, the web interface to use the data mine, the lessons learned in the creation and use of the data mine, the diverse domains from which users have come, and some of the applications for which the data have been used.