marriage into the Anckarswärd family in 1842, Gripenstedt became affiliated with the "liberal landowners'"-faction of the parliament, led by Carl Henrik Anckarswärd. In the end of 1841, Gripenstedt was elected to the parliament's powerful Committee on the Constitution, which at this time worked on a new representative reform. As opposed to the conservative group of the parliament, Gripenstedt was a strong adherent of free elections and general suffrage long before this was realized in Sweden. During start of the Riksdag of 1847, Gripenstedt was elected to the Committee of the State. As a trustee of Carl Henrik Anckarswärd, and later as the owner of estates such as Nynäs Castle in Södermanland, Gripenstedt became a successful entrepreneur within the grain exports and iron industry. In 1848 Gripenstedt was selected, to many's surprise, by King Oscar I to serve as Minister without Portfolio () in his cabinet. The post was first offered to the conservative Jacob Nils Tersmeden, who declined, and King Oscar wanted to rejuvenate his cabinet why he selected Gripenstedt instead. Gripenstedt also served as acting Minister for Finance from 10 January to 21 October 1851. On 28 May 1856 he was appointed as (permanent) Minister for Finance. Influenced by French liberal thinkers such as Alexis de Tocqueville and Frédéric Bastiat, Gripenstedt was a leading proponent of free trade and other liberal reforms. He succeeded in getting the Swedish parliament to gradually abolish tariffs and reduce customs duties. In 1865 he signed trade agreements with France, the German Customs Union and Prussia, which resulted in greatly reduced customs duties on many products. His optimistic descriptions in the Swedish parliament in 1857 of the economic situation of the country, the so-called "flower paintings" (), paved the way for a fast expansion of the Swedish railroad network, which was financed by loans on the international market. Against the opposition, Gripenstedt insisted that national railroads should not be profitable as a business, but that they as an infrastructure should contribute to the profitability of other investments and to the country as a whole. Gripenstedt opposed an activist foreign policy, which he saw as a threat to the economic stability of the country. As the Danish-German conflict over the Schleswig-Holstein Question grew more tense, Gripenstedt and then Prime Minister for Justice Louis De Geer (also a devoted liberal) stopped King Charles' plan for Swedish military support in the upcoming war. Following his retirement as