In 1886 Don Juan Bautista Grau and Vallespinós, a native of Reus, took possession of the diocese of Astorga, residing in the former episcopal palace, and on December 23 of that same year the primitive palace burst into flames. When the place of diocesan architect for the construction of the new palace is vacant, Bishop Grau proposes his countryman Antoni Gaudí and Cornet.
Gaudí is going to take charge of the works of 1889-1893.
In December 1888, Gaudí traveled to Astorga to learn about the plot and the architectural environment. In February of 1889, the Ministry gives the approval to the project, leaving the works to public auction and adjudging them to the contractor D. Policarpo Arias in the amount of 168.520 pts.
On June 24, 1889, onomastics of the prelate, the first stone is placed. They planned to finish the works of the Palace in June 1894, but the bishop died in 1893 and this fact radically changed the course of the works, paralyzed by the antagonism between Gaudí and the Diocesan Board.
Finally, Antonio Gaudí will resign as architect director, very upset by the treatment received and stating: “They will be unable to finish it and leave it interrupted.”
In 1905, Julián de Diego y Alcolea governed the diocese of Astorga and tried to convince Gaudí of his return to the Palace works but he did not succeed. The temple of the Holy Family required all its attention and time.
Architect Ricardo García-Guereta, who was a diocesan from León, was named architect, finishing the works on October 12, 1913 and being Bishop D. Julián de Diego y Alcolea. Later with Bishop Antonio Senso Lázaro, the lack of concern for the palace is evident.
During the Civil War it is used as barracks and offices of the Falange and accommodation of national forces.
In 1956, Mr. José Castelltort, natural bishop of Igualada, made the last adaptations on the second floor of the building with the intention of inhabiting it as soon as possible, but his sudden death prevented it.
He will succeed him in the episcopal chair D. Marcelo González Martín, who decided to permanently reside in the Seminary and dedicate the Palace to the headquarters of the Museum of Roads, which will open to the public in 1964.