The Catalyst Scholarship Program at Hunter College of The City University of New York (CUNY) was established with a four-year award from the National Science Foundation (NSF) to fund scholarships to 40 academically talented but financially disadvantaged students majoring in four disciplines of science, technology, engineering and mathematics (STEM). Scholarships were awarded to students in their junior or senior years majoring in computer science, geosciences, mathematics and physics to create two cohorts of students that spend a total of four semesters in an interdisciplinary community. The program included mentoring of undergraduate students by faculty and graduate students (peer-mentoring), a sequence of three semesters of a one-credit seminar course and opportunities to engage in research activities, research seminars and other enriching academic experiences. The program resulted in increased retention rates relative to institutional averages. This article describes the program, presents an overview of accomplishments and lessons learned, results of an assessment performed at the end of the fourth year of the award and a discussion of the process of establishing the program, from the original plans to its implementation at the institution. [The manuscript was partially written at the GAIN 2013 Workshop funded by NSF Award Numbers 0620087 to Suzanne O'Connell and 0620101 to Mary Anne Holmes.]