The history of this estate dates back to 1201. At least, that is the assumption, as there is nothing more than a written mention in the Historia nobilis parthenonis Heinsbergensis of 1772 to go on. In that work, Provost Friedrich Keetz wrote that Gosewijn IV of Valkenburg took the decision in 1202 to found a monastery near the grave of the hermit Gerlach, who had died circa 1165. The grave of this man drew many pilgrims, and Gosewijn wanted to provide good accommodation for them. The lord of Valkenburg appealed to the young order of Norbertines to fulfil his plan. After all, his grandfather had founded a Norbertine monastery in Heinsberg circa 1140. The monastery was originally a double monastery, for both monks and nuns.
Until approximately 1257, the monastery in Houthem was under the control of the provost of Heinsberg. After 1257, the monastery gained its own provost. As early as the first centuries of its existence, the monastery had great appeal for those of distinguished descent. In 1345, Dirk IV, lord of Valkenburg, dubbed the monastery a convent for noble ladies. This was to remain the case until its closure in the eighteenth century.
The monastery was not spared during the turbulent years of the religious wars. In 1574, the monastery buildings were devastated by the troops of Louis of Nassau. Sources dating from 1581 state that the monastery was burned down twice. There was a lull in the war in 1661, when a treaty was concluded between the belligerent parties regarding the division of the territory. It was determined that the monastery of Saint Gerlach would remain under Spanish sovereignty. A new arrangement came into force later. In 1786, the treaty of Fontainebleau determined that the monastery would no longer fall under Spanish authority but under Dutch rule instead. On 6 September 1786, the sisters left the monastery definitively. In 1795, the French annexed the Austrian Netherlands, and a few years later they closed all monasteries and the properties were sold to third parties.
It was the manager of the affairs of the Norbertine nuns, the notary Schoenmaeckers from Raar, who bought the monastery and the church. It was to become the family estate. The former monastery properties were leased out and the provost building was converted into a noble residence. The church was given to the municipality of Houthem and was to become the new parish church in 1808. The mansion of Saint Gerlach was first inhabited by the Corneli family and later by the noble De Selys de Fanson family.
In 1979, the last inhabitant of the mansion - Robert De Selys de Fanson – bequeathed the mansion and the outbuildings to the church council of Houthem. From then on, the property was unoccupied. Consequently, a number of outbuildings ended up in a very dilapidated condition.
Camille Oostwegel first submitted his idea for a luxurious hotel/restaurant at the St. Gerlach estate to the church council as early as 1979. He made contact again in 1986, when he explained the outlines of the plan to the Stichting Behoud St. Gerlach (Foundation for the Preservation of St. Gerlach) which was established in 1988 for the purposes of the preservation of the estate. In 1990, they reached an agreement in which the starting points of the plans were set down.
Once the various bottlenecks had been resolved, including the matter of the Erens family lease, the agreement of the church council and the bishopric, the acquisition of definitive grant pledges and finding a use for the convent building and the granary, the comprehensive agreement was signed in 1994.
Between 1995 and September 1997, the estate was restored and given its new role as luxurious hotel with 58 rooms, 2 restaurants, the Kneipp S.P.A., various conference rooms, a swimming pool, park and 39 hotel apartments. These apartments are run by private individuals. In return, the parish gained a new presbytery, a museum with a treasury for St. Gerlach, a new catechism room, sacristy and a new Gerlach chapel.
Château St. Gerlach has welcomed many well-known guests in the few years since its opening, most notably the American President, G.W. Bush, in 2005.