[Sister Havana]

My alma mater, Indiana University, has several single letter chapters:

Delta Gamma (Theta)
Delta Zeta (Epsilon)
Kappa Alpha Theta (Beta)
Kappa Kappa Gamma (Delta)
Sigma Delta Tau (Upsilon)

Single letter chapters now closed:
Sigma Kappa (Tau)
Theta Phi Alpha (Zeta)