I did Delta Tau Delta for you, DeltAlum.
I have no idea how naming chapters was done for Delt
but this is what I found:
12 active out of 37 but Delt's another one that has several very old double-letter chapters (i.e. Beta Lambda @ Lehigh 1874 is active).
Theta – Bethany College 1859
active
Gamma – West Liberty College 1859
Gamma – Washington and Jefferson College 1861
active
Beta – Ohio University 1862
active
Alpha – Allegheny College 1863
active
Kappa – Poughkeepsie Collegiate Institute 1865
Lambda – Monmouth College 1865
Mu – Waynesburgh College 1865
Mu – Ohio Wesleyan University 1866
active
Kappa – Hillsdale College 1867
Iota – Jamestown Collegiate Institute 1868
Chi – Westminster College 1868
Lambda – Lombard College 1869
Delta – University of Michigan 1871
Rho – Lake Shore Seminary 1871
Phi – Hanover College 1872
Tau – Pennsylvania State 1872
active
Chi – Franklin College 1872
Iota – Michigan State 1872
Eta – Buchtel College 1873
Xi – Simpson College 1873
Rho – Stevens Institute of Technology 1874
active
Tau – Franklin and Marshall 1874
Nu – Lafayette College 1874
Chi – Iowa Wesleyan 1874
Sigma – Mt. Union College 1875
Epsilon – Albion College 1876
active
Psi – Wooster College 1879
Upsilon – Rensselaer Polytechnic Institute 1879
active
Omicron – University of Iowa 1880
Chi – Kenyon College 1881
active
Zeta – Case Western Reserve University 1882
active
Sigma – Williams College 1891
Phi – Washington and Lee University 1896
Omega – University of Pennsylvania 1897
active
Chapters that were originally Rainbow
Pi – University of Mississippi 1848 (1886)
Lambda – Vanderbilt University 1881 (1886)