Railway station in Travelcard Zone 2 opened 1904.
Between 1922 and 1948 the station name was Canonbury & Essex Road. The name reverted to the original form in 1948. It is the only deep-level underground station in London served exclusively by National Rail trains. Between 1933 and 1975 the station was operated as part of the London Underground, as a short branch of the Northern line.
The Wikipedia page, including future proposals for the station is [1]. The TfL page is [2].