A recurring request from the Geospatial Centre’s (GC) clients is the capability to visualize and access geospatial, and other cartographic collections and indexes online. From mounting interactive air photo indexes, to uploading local historical maps, to offering a one stop shop for municipal open data, the GC has recently created three interactive mapping web projects – all to aid in the discovery and access of cartographic and geospatial collections: Waterloo Region Historical Maps, using Google Earth Application Programming Interface(API) http://www.lib.uwaterloo.ca/locations/umd/digital/historicmaps.html Interactive Airphoto and Photomap Index Maps, using OpenLayers http://www.lib.uwaterloo.ca/locations/umd/photos/airphoto_index.html Open Data Websites, using SIMILE Exhibit http://www.lib.uwaterloo.ca/locations/umd/digital/opendata.html Have you ever wondered how these types of mapping applications work? How are they built? Is it something that you do? After a quick demonstration and a brief introduction to several open source mapping applications, the presentation will summarize the steps GC staff took in building three of their recent interactive mapping projects, including how to prepare the data files, a quick look at the source code, and how to update and add new records. Future interactive mapping projects will also be shared.