| 1868 |
The ‣ to ‣ (Metropolitan Railway) line extends to ‣. The District Railway opens its new line from ‣ to ‣ at the same time |
| 1884 |
The District Railway line finally extends to Mark Lane (now ‣). It meets the Metropolitan Railway line to create a full circle |
| 1905 |
The line is electrified |
| 1933 |
Metropolitan Railway and District Railway become part of the London Passenger Transport Board |
| 1936 |
The 'Circle line' name appears on a poster for the first time |
| 1949 |
The Circle line gets its own line on the Tube map |
| 2009 |
The Circle line is broken and replaced by and end-to-end service |