The administrative centre was the town of Finnsnes, where the Gisund Bridge connects Senja to the mainland on Norwegian County Road 86.

Other villages in the municipality included Aglapsvik, Gibostad, Botnhamn, Fjordgård, Finnfjordbotn, Husøy, Langnes, Laukhella, Silsand, and Rossfjordstraumen.

On 1 January 1871, a small part of Lenvik (population: 70) was transferred to the neighboring Malangen Municipality.

The new municipality would encompass the whole island of Senja plus part of the mainland located between the Gisundet strait and the Malangen fjord.

On 6 January 1908, a royal resolution changed the spelling of the name of the municipality to Lenvik, removing the definite form ending -en.

The official blazon is "Azure, three oars bendwise Or, blades to the chief" (Norwegian: I blått tre skråstilte gull årer med bladene opp).

This means the arms have a blue field (background) and the charge is three oars laying diagonally with the blades at the top of the shield.

The blue color in the field and the oars were chosen as a symbol for sailing and shipping along with the fishing industry which is the main form of income in the municipality.

The Gisundet strait ran north–south through the center of the municipality with only one road crossing, the Gisund Bridge.

The municipal council (Kommunestyre) of Lenvik was made up of 31 representatives that were elected to four year terms.