The fertile soil of Calauan attracted attention of Captain Juan de Salcedo, when he passed through Laguna and Tayabas (now Quezon) on his way to Bicol Region in 1570. Ten years later, Spanish authorities established a town government two kilometers from the site of the present Poblacion, in what is now Barrio Mabacan. They called the townsite “Calauan” (tagalong word for rust). Following an epidemic in 1703, the town was moved to its present site at the fork of three roads—now to the southwest leading to San Pablo City, the other southeastward to Sta. Cruz, the provincial capital, and the third going North to Manila.

It is said that a rich woman of Calauan paid for the construction of a concrete church in 1787, and the archbishop in Manila installed San Isidro Labrador and San Roque, whose feast day of May 15, as Patron Saint of the town. At the turn of the 18th century, when Bay was designated as the provincial capital of Laguna, Calauan became a sitio of Bay. Merchants going to Southern Luzon usually passes through Bay and Calauan. One of them, an opulent Spaniard by the name of Iñigo in 1812 bought large tracts of land in Calauan. The landholdings of Iñigo and, later, of his heirs were so vast that many portions were still unsettled. The property was and still is, known as Hacienda Calauan. About a century later, the people of Calauan fought a “guardia civil” during the Philippine Revolution. Basilio Geiroza (better known as Cabesang Basilio) and his men routed a battalion of “guardia civiles” in a five-hour battle in Bario Cupangan (now Lamot I) in December 1897. During the subsequent Philippine-American hostilities, Calauan patriots fought numerically superior forces of General Otis in Barrio San Diego of San Pablo. With the establishment of civilian authority in Calauan in 1902, the Americans assigned Mariano Marfori as first “presidente”. Hacienda Calauan finance the construction of a hospital in 1926, and Mariano O. Marfori, Jr. son of the first municipal presidente, as the hospital director and the resident physician, respectively. (The hospital, unfortunately, was destroyed in World War II and has not been rebuilt since then).

In 1939, by the request of President Quezon, Doña Margarita Roxas vda. De Soriano, granddaughter of the Spaniard Inigo, subdivided Hacienda Calauan and sold it to the tenants, part of what remained was converted into a rest house and a swimming pool and it became one of the tourist attractions until 1956.

The town got its name from the term “Kalawang” which means rust. It was claimed that for centuries lumps of rust surfaced and drifted gently on a body of water called Macalawang Spring. This spring was situated nearly three (3) kilometers from the town proper.

Another interesting premise upon which the name Calauan was chosen has a little story to tell… During the early part of Spanish sovereignty over the Philippines, there was a village located west of the town where an old man found a cross made of stone. Since Christianity was being introduced in the town the people felt they should treat such cross with reverence. They held a mass at the spot where the stone cross was found. To the surprised of all, during the celebration of the mass, water sprang out from the exact place where the stone was located. The water was yellowish and “rusty”. To commemorate this mysterious event, the people built a church on this site. They saw to it that altar was constructed right on the spot where the water had sprung out. The village had grown larger and then populated and then became the town proper. Being mostly farmers, the people chose to honor San Isidro Labrador and San Roque as their Patron Saints. They celebrate the PINYA FESTIVAL every 15th of May.