[1] In Bydgoszcz, Louis and his family lived successively at: In 1878, at the age of 28, Lewis entered the City Council and remained its member continuously until 1890.

In the political arena, Aronsohn joined the Free-thinking People's Party (German: Freisinnige Volkspartei): he chaired its local city club.

He had been regularly criticizing the policy of the Prussian Settlement Commission, which bought Polish estates in the Provinces of Posen and West Prussia: from his point of view, this scheme provided Poles the financial means to settle in towns.

[4] In April 1914, he unsuccessfully suggested to use a restrictive clause for the government aid of home ownership in order to exclude Poles from the funding.

[citation needed] Aronsohn was also the founder, on 29 August 1891, of the Bromberger Schleppschiffahrt Aktien Gesellschaft, future Bydgoszcz Shipping and Towing joint-stock Company (today "Żegluga Bydgoska").

The main shareholders were: Louis, Heinrich Dietz and other city councilors (Fritz Kleindienst, Karl Wenzel and Emil Werckmeister).

[7] As such, he reinvigorated the construction project of a new synagogue in the city:[8] the foundation stone was laid on 21 October 1882 and the edifice was solemnly consecrated on 9 September 1884.

[10] Furthermore, Louis participated to other associations:[10] He was active in projects dealing with very diverse domains: natural science, art, singing, engineering or literature.

[10] He donated a plot of land to the city for the construction of a care and education facility for small children, (German: "Kleinkinderbewahranstalt")[11] completed in 1910.

Aronsohn's last donation to the city amounted to German Mark 100,000: it was intended to cover the costs of building an indoor swimming pool.