You won't find one definitive list that everyone accepts. However, you can find comprehensive lists by searching through these resources:
* Massachusetts Department of Higher Education (DHE): Their website is a good starting point. While they may not have a single, readily downloadable list of *every* institution, they will have listings of public colleges and universities, and likely links to data that could help you compile your own list.
* The National Center for Education Statistics (NCES): This federal agency collects data on all colleges and universities in the U.S. Their website allows you to search and filter by state (Massachusetts), which will give you a substantial list.
* Online directories: Websites like Peterson's, US News & World Report, and Niche all maintain databases of colleges and universities, allowing you to filter by state. These lists might not be entirely exhaustive, but they provide a considerable number of institutions.
By combining information from these sources, and making decisions on what constitutes a "college" or "university" in your criteria, you can create your own list and arrive at a number. Keep in mind that the number will vary depending on your definition.