Verizon Delaware LLC, formerly The Diamond State Telephone Company, is the Bell Operating Company of Delaware, and small parts of southeastern Pennsylvania. Founded in 1897, it became a part of the Bell System in 1905.^[1] When the AT&T breakup occurred in 1984, DST became managed by the Regional Bell Operating Company Bell Atlantic.^[1] In 1994, Bell Atlantic chose to "unify" its brand by legally renaming all of its telephone companies — including Diamond State Telephone to "Bell Atlantic – Delaware, Inc".

After the 2000 merger with GTE, Bell Atlantic – Delaware, Inc. became known as Verizon Delaware, Inc., and later as Verizon Delaware LLC.