When at first you succeed, what comes next? Twelve academic libraries are collaborating on a data discovery portal interface and harmonized metadata schema for geospatial data from a wide range of academic and government sources including digitized historic maps. Following the successful 2016 launch of the Big Ten Academic Alliance Geoportal (https://geo.btaa.org/), we now turn our attention to progressing into a sustainable growing project.This presentation will detail the Geoportal's content and interface and the collaboration structure of the project. Additionally, we will discuss a novel user study with results showing interesting differences between users of varied expertise, which fueled changes in the Geoportal interface. Attendees will be oriented to various considerations involved in establishing and maintaining an aggregation of geospatial information from diverse sources, including the access stability issues involved in data hosted by local governments, the generation of metadata for geospatial datasets and digitized maps, and project structure evolution. We hope our experiences will inspire others toward similar kinds of large-scale collaborative projects.