After the founding of chapters at Cincinnati, Western Reserve, and Ohio University, the fraternity continued to grow as outlined below:

1850-1900: The Civil War caused the greatest crisis in the history of Beta Theta Pi. The war threatened the life of more than half of the 24 chapters in existence in 1860, with the functioning chapters being reduced by 1864 to those at Miami, Western Reserve, Jefferson, Washington, Indiana Asbury (DePauw), Ohio Wesleyan, Wabash, Hanover, Ohio, Knox and Indiana. The war threatened the fundamental principle of brotherhood.

The fraternity continued to expand steadily until in 1879 a union with Alpha Sigma Chi was approved adding five new chapters at Rutgers, Cornell, Stevens, St. Lawrence and Maine. This provided the fraternity with an important presence in the East that it had previously lacked. By 1889 another union was consumated with The Mystic Seven Society adding chapters at Davidson, North Carolina, and Virginia.

1900-1950: By the turn of the century, two important features of Beta Theta Pi had become apparent. The first — Beta character — had already manifested itself in stories such as that of John Holt Duncan and the men of the Michigan chapter who refused to forsake their membership and their badge.

In 1906 a significant milestone in Beta history occured with the chartering of its first chapter in Canada. The Theta Zeta chapter at the University of Toronto was established making Beta Theta Pi an international fraternity.

1950-present: With the establishment of the Administrative Office and appointment of an administrative secretary in 1949, the stage was set for spectacular growth and a solid future for Beta Theta Pi and her fraternal colleagues in the years ahead. Almost immediately, however, the Korean War took a tragic toll on the chapters, followed by the emergence of more independent collegians, quick to express themselves over the Vietnam War, often joined by their own faculties. Nonetheless, the Beta spirit endured, grew stronger and, by the end of the 20th century, a renewed commitment to the Beta principles — the Men of Principle initiative — was embraced by Beta Theta Pi, born of necessity and nurtured by yet another evolution of young men who yearn for excellence and thrive on brotherhood.