Original: On 20 February 1802 Rheinfelden was made a district capital of the newly created Canton of Fricktal, (Pincipality of Frickgau), joining the Helvetic Republic in August, the point at which the city became decisively Swiss.
Simplified: On 20 February 1802, Rheinfelden was made the capital city of the new Canton of Fricktal, joining the Helvetic Republic in August, the point at which the city became mostly Swiss.