The town, founded in the Middle Ages, lies in the Seetal valley, about 3 kilometres south of the Aare river.

A Neolithic grave field of the Cortaillod culture has been discovered on the Goffersberg (close to the Lenzburg Castle) dating from 4300 - 3500 BCE.

The Reformation was carried out simultaneously with the rest of the region in 1528, and the economy started to transform slowly from an agrarian to a more industrial one in the 16th century.

In 1830, a series of meetings were held in Lenzberg to discuss changing the cantonal constitution.

When peaceful negotiation with the cantonal authorities in Aarau failed to produce results, Johann Heinrich Fischer from Merenschwand called for a rebel militia from the Freiämter to force the government to change, in what was known as the Freiämtersturm.

At Lenzberg, about 100 government soldiers formed to resist the militia, and brought their guns in position.

On 6 September 1877 the Schweizerische Nationalbahn opened a line from Wettingen to Zofingen as part of a plan to connect Singen, Germany and Lake Geneva in competition with the established railway companies.

The bankruptcy of the Nationalbahn brought Lenzburg to the brink of economic ruin, as the city itself was heavily involved in financing it.

Lenzburg lies on the small river Aabach, at the northern edge of the Seetal.

Of the rest of the land, 3.2 km2 (1.2 sq mi) or 28.2% is settled (buildings or roads), 0.06 km2 (15 acres) or 0.5% is either rivers or lakes.

[9] The age distribution, as of 2008[update], in Lenzburg is; 731 children or 9.1% of the population are between 0 and 9 years old and 845 teenagers or 10.5% are between 10 and 19.

[11] About 36.2% of the total households were owner occupied, or in other words did not pay rent (though they may have a mortgage or a rent-to-own agreement).

Above the city is the Burghalde at Schlossgasse 21 and Lenzburg castle (which is over a prehistoric settlement and contains the Cantonal Museum).

Two other ancient sites, Goffersberg (a neolithic graveyard) and Lindfeld (a Roman Vicus, theatre and burial ground), are included in the list.

[15] The undisputed landmark of the city is the Lenzburg Castle, built in the 11th century and since enlarged on several occasions.

The old part of the town at the foot of the hill is U-shaped and in very good condition, consisting of a main road with two parallel alleys and another lane.

Some notable buildings in and around the old town include: Lenzburg is an important economic centre, containing over 600 enterprises, of which about 80% in the service sector.

The majority of businesses are in the small and medium enterprise bracket, but a number of international companies are established in Lenzburg, such as the multinational ABB and the meat processing plant Traitafina.

A partially underground road named "Kerntangente" was constructed to draw through-traffic away from the city centre.

The local transit Regionalbus Lenzburg leads to Brunegg, Dintikon, Möriken-Wildegg, Schafisheim and Seengen.