The two-century thing intrigued me, so I went looking...
First commercial telegraph system looks to have been 1837, for railways comms between Euston and Camden. This failed to win the contract, losing to a pneumatic+whistle system!
First transatlantic telegraph line was 1858, though it only worked for a few weeks (at 0.1 words per minute). A durable replacement happened in 1866, working at 8 words per minute.
Surprisingly, the first transatlantic telephone cable only happened 100 years later, 1956, with 36 channels, carried over coax pairs.
As ever, bandwidth development over the material seems to be key, not the material itself.