Mr. Watson — come here — I want to see you.
10 March 1876 · 5 Exeter Place, Boston, MA
The patent
Bell had been granted US patent 174,465 three days earlier, on 7 March 1876. The 10 March demonstration proved the concept the patent described.
The century that followed
By 1900, ~600,000 US phones. By 2000, more phone lines than people. By 2020, more mobile devices than humans.
Bell cried out to Watson because he'd just spilled acid on himself in a moment of panic.
Bell's own laboratory notebook entry from March 10, 1876 describes only a successful transmission test — no acid spill. The dramatic detail first appears in Watson's retellings roughly fifty years later.
Bell invented the telephone in a single flash of insight that afternoon.
This was the culmination of months of work on a "harmonic telegraph," and Bell had already been granted the telephone patent three days earlier, on March 7.