Frank Stella's "Irregular Polygons" series, developed during 1965-1966, represents a crucial phase in his artistic development, moving beyond the minimalist restraint of his earlier works into a realm that explores vibrant color, dynamic shapes, and the expansion of pictorial space. This series is composed of eleven compositions, each executed in four different color schemes, introducing an element of variation and exploration into Stella's work that was less pronounced in his previous series. The incorporation of color marks a significant departure from his earlier monochromatic pieces, adding a new dimension of visual interest and complexity​ (The Montgomery Fellows)​​ (UO Blogs)​.

Stella's shift to using asymmetrical canvases in the "Irregular Polygons" series was a move away from the symmetrical, geometric forms that characterized his work in the early 1960s. This choice underscored his growing interest in challenging traditional notions of pictorial space and compositional balance, engaging the viewer in a more dynamic interaction with the artwork. The use of oil paint on large canvases, approximately 7 feet by 10 feet, stretched over four-inch wooden frameworks, gives these pieces a significant physical presence and a rich texture that enhances their visual impact​ (UO Blogs)​.

The "Irregular Polygons" series is not just a departure in terms of form and color but also represents Stella's broader interest in expanding the possibilities of abstract art. By exploring the relationships between different shapes within each composition, Stella creates a sense of movement, tension, and balance that invites viewers to engage with the works in a more immersive way. This series stands as a testament to Stella's creative evolution, showcasing his ability to innovate within the constraints of minimalism and to push the boundaries of abstract painting towards new horizons​ (UO Blogs)​.

Stella's time at Dartmouth College, coinciding with an exhibition of the "Irregular Polygons" at the Hood Museum of Art, underscores the significant impact of this series on his career and its reception in the broader art world. The fellowship provided him with an opportunity to interact with students and faculty, offering insights into his creative process and the conceptual underpinnings of his work during this transformative period​ (The Montgomery Fellows)​.

The "Irregular Polygons" series, therefore, marks a pivotal moment in Frank Stella's artistic journey, reflecting both a deepening of his engagement with the formal aspects of painting and a stepping stone towards the more elaborate, sculptural, and architectural explorations that would characterize his later work.