It has an area of 145,142 sq. km., with a population of 1,100,000 inhabitants, of whom 950,000 are Catholics. It comprises 59 parishes, served by 75 diocesan priests and 65 religious; it has one seminary, 24 male religious communities and 64 female (Ann. Pont., 1951, p. 269).
The diocese was created by Pius XI with the apostolic constitution *Novilis Argentinae nationis* of 20 April 1934, by separating a group of parishes from the diocese of La Plata and erecting as its cathedral the parish church of the Blessed Virgin Mary of Mercy in Mercedes. The diocese is a suffragan of Buenos Aires. Its first bishop was Msgr. Giovanni Chimento; the present ordinary is Msgr. Annunziato Serafini.
BIBL.: AAS. 27 (1935), pp. 257-63. Enrico Josi