[dukedg]

(Info courtesy of ajuhdg's fabulous list in our forum.) Since the single-letter naming convention allowed a new chapter to use a closed chapter's letter, the ratio is up for interpretation. I would say 22/34.

Active (21)
Eta-Akron, OH (1879)
Omega-Wisconsin (1881)
Sigma-Northwestern, IL (1882)
Theta Beta-Case Western Reserve (2004) (formerly Theta II, Adelbert College 1883-1888)
Lambda-Minnesota (1883)
Zeta-Albion, MI (1883)
Chi-Cornell, NY (1885)
Xi-Michigan (1885)
Phi-Colorado (1886)
Tau-Iowa (1886)
Kappa-Nebraska (1888)
Theta-Indiana (1898)
Rho-Syracuse (1901)
Beta-Washington (1903)
Iota-Illinois (1906)
Gamma-California, Berkeley (1907)
Omicron-Adelphi, NY (1908)
Mu-Missouri (1909)
Epsilon-Ohio State (1911)
Pi-Montana (1911)
Nu-Idaho (1911)

Inactive (12)
Psi (I)-Lewis School, MS (1873-1889)
Theta (I)-Fairmont College, TN (1877-1880)
Chi (I)-Water Valley Seminary, MS (1877-1880)
Phi(I)/Phi Alpha-Franklin College, IN (1878-1885)(1995)
Upsilon (I)-Bolivar College, TN (1878-1881)
Delta (I)-Trinity College, TX (1880-1881)
Delta (II)-Hanover College, IN (1881-1887)
Pi (I)-Fulton Synodical College, MO (1882-1885)
Alpha-Mount Union, OH (1882-1908)
Upsilon (II)-St Lawrence, NY (1884-1887)
Psi (II)-Goucher, MD (1891-1950)
Upsilon(III)-Stanford (1897-1944) (?-1999)

Active under Non-Single-Letter Chapter (1)
Delta (III)-Southern California (1887-1897)