19 January 1844,
Tolosa was declared the capital of Gipuzkoa by royal decree. Gipuzkoa had no fixed capital before. In 1472, a rotating procedure was established to hold the General Boards among the villas, and in the early nineteenth century it was decided to rotate the headquarters of the corridor between Azpeitia, Azkoitia, San Sebastián and Tolosa. However, in 1844, due to the restoration of the Fueros and taking advantage of the strength of the latter in the controversies between progressive and moderate in Spain, Tolosa was designated capital. In 1854, with the arrival of the progressives to power, the capital moved to San Sebastian.
Source:
Virtual Museum of Gipuzkoa, What capital: Tolosa and Donostia, by memory