Yes, there were glass insulators along telegraph lines

"Long before the modern era of computers, cellphones, smartphones, fiber-optic cables and the internet, long distance electric/electronic communication consisted primarily of the telegraph and telephone.   The electric telegraph (in the United States) was developed by Samuel Morse in 1837, and the first message was sent by Morse in 1838. The telephone was invented by Alexander Graham Bell in 1876.

As time went on, networks of “open wire” telegraph lines, and later, telephone lines, were developed and built throughout the country, and these lines required the installation of insulators.  Insulators were necessary by serving as a medium for attaching the wires to the poles, but much more importantly, they were required to help prevent electric current loss during transmission. The material, glass, is itself an insulator (not a “conductor” or “transformer” as insulators are often incorrectly labeled in antique malls and flea markets).

Both glass and porcelain insulators have been used since the early days of the telegraph, but glass insulators were generally less expensive than porcelain, and were normally used for lower-voltage applications. The oldest glass insulators date from about 1846.'

Read more about the glass insulators -> https://glassbottlemarks.com/general-overview-glass-insulators/

Found somewhere along the SNETT trail

Yes, there were glass insulators along telegraph lines