Clockwise from the northeast, beginning at the German shore of the Flensburg Firth, the following communities in Schleswig-Flensburg district and Denmark's Southern Denmark Region all border Flensburg: Glücksburg (Amt-free town), Wees (Amt Langballig), Maasbüll, Hürup, Tastrup and Freienwill (all in Amt Hürup), Jarplund-Weding, Handewitt (Amt Handewitt), Harrislee (Amt-free community) and Aabenraa Municipality on the Danish shore of the Flensburg Firth.

Historians presume that there were several reasons this spot was chosen for settlement: Herrings, especially kippered, brought about the blossoming of the town's trade in the Middle Ages.

On 28 October 1412, Queen Margaret I of Denmark died of the plague aboard a ship in Flensburg Harbour.

The church hospital "Zum Heiligen Geist" ("To the Holy Ghost") stood in Große Straße, now Flensburg's pedestrian precinct.

After the fall of the Hanseatic League in the 16th century, Flensburg was said to be one of the most important trading towns in the Scandinavian area.

The town was becoming Protestant and thereby ever more German culturally and linguistically, while the neighbouring countryside remained decidedly Danish.

Cane sugar was imported from the Danish West Indies (now the US Virgin Islands) and refined in Flensburg.

The SSW political party representing the minority usually gains 20–25% of the votes in local elections, but not all its voters are Danes.

Before 1864, Danes consisted of the vast majority, which belonged to what is now the minority; even today there are many Danish surnames in the Flensburg telephone directory (Asmussen, Claussen, Jacobsen, Jensen, Petersen, etc.).

However, the upper classes at that time, comprising merchants, bureaucrats, academics, and the clergy, were predominantly German.

In return for this pro-German vote, Flensburg was given a large hall, the "Deutsches Haus", which the government endowed as "thanks for German loyalty".

During the Second World War, the town was left almost unscathed by the air raids that devastated other German cities.

But in 1943, 20 children died when a nursery school was bombed, and shortly after the war ended, an explosion at a local munitions storage site claimed many victims.

In 1945, Admiral Karl Dönitz, who was briefly President (Reichspräsident) of Nazi Germany after Adolf Hitler appointed him his successor and then killed himself, fled to Flensburg with what was left of his government.

[4] After the Second World War, the town's population broke the 100,000 mark for a short time, making Flensburg a city (Großstadt) under one traditional definition.

In the years after the Second World War, South Schleswig, and particularly Flensburg, had a strong pro-Danish movement connected with the idea of the "Eider Politics".

Until 1870, figures are mostly estimates, and thereafter census results (¹) or official projections from either statistical offices or the town administration itself.

The border shops may sell canned beer to Scandinavia residents without paying deposits as long as it is not consumed in Germany.

Since that time, the former official has been called the Stadtpräsident ("Town President"), and is likewise chosen by the council after each municipal election.

On 14 November 2004, the independent candidate suggested by the CDU, Klaus Tscheuschner, was elected to replace Stell with 59% of the vote.

The most recent city council election was held on 14 May 2023, and the results were as follows: The result of the election held 6 May 2018 were as follows: Flensburg's coat of arms shows in gold above blue and silver waves rising to the left a six-sided red tower with a blue pointed roof, breaking out of which, one above the other, are the two lions of Schleswig and Denmark; above is a red shield with the silver Holsatian nettle leaf on it.

The lions symbolize Schleswig, and the nettle leaf Holstein, thus expressing the town's unity with these two historic lands.

The coat of arms was granted the town by King Wilhelm II of Prussia in 1901, and once again in modified, newly approved form on 19 January 1937 by Schleswig-Holstein's High President (Oberpräsident) Flensburg is twinned with:[13] The town has a well-established Combined Heat and Power and District Heating scheme, installed between 1970 and 1980.

West of Flensburg runs the A 7 Autobahn, leading north to the Danish border, whence it continues as European route E45.

Local transport is provided by several buslines, including Aktiv Bus GmbH and Allgemeinen Flensburger Autobus Gesellschaft (AFAG).

The tramway, which opened in 1881 to horse-drawn trams, was electrified in 1906, and at one point ran four lines, was replaced by buses in 1973.

The "Offener Kanal" ("Open Channel") shows programmes made by local citizens seven days a week, mostly in the evenings, and can also be seen on cable television.

Virtually unscathed in the Second World War, Flensburg, like other places in Germany, adopted a policy of getting rid of old buildings and rebuilding in the style of the time.

Lack of money limited this trend in Flensburg, but before the policy ended in the late 1970s, countless old buildings had been demolished in the north and east Old Town, to be replaced by newer structures.

Despite great losses, Flensburg still has a compact, well-preserved Old Town in the valley with good additions to what was built in the founders' time on the surrounding heights.