The increase in productivity and the consequent development gradually attracted migrants from all over the country. The bulk of these migrants were from Visayas. With the eruption of Mt. Hibok-Hibok, migrants from the Camiguin Island also came.
The influx of migrants not only increased the population in the early settlement but also added vigor to its economic life. Thus, as soon as the Spaniards came to Mindanao, the Salay settlement was among the first to be brought under Hispanic control. Hispanization of Salay became complete when the last among the Higa-onon Chieftains, Datu Tala-ta, was baptized into Christianity by Rev. Father Parache, a Spanish missionary. Datu Tala-ta carried the Christian name Captain Rufino Gonzales.
The current Poblacion of Salay was developed a little later by the Spanish Administrators as attention then was focused on fortifying the Binuangan Area (then called DaangLungsod) from sea-borne moro raids. As soon as danger from pirate attacks simmered, the Spaniards saw the potentials of the current SalayPoblacion as strategic seat for a new Municipal Government that they were then contemplating of establishing at Binuangan. It was Captain Jacinto Zagado who donated a parcel of his irrigated land for use as public plaza, site of the Municipal tribunal and other government buildings. Subsequently, Spanish administrators worked towards establishing a permanent community. At the time, the Spaniards did initial municipal planning.
The elevation of Salay into a full-pledged municipality was due to the cooperative efforts of the Salay community, however, singled out as a key mover in these efforts was a civic organization formed deliberately for the purpose of working for the creation of a separate Salay Municipality. The organization was identified as the El ProgresoSalayano. Under the leadership of Mr. Bruno Salvaña, the organization lobbied in congress for the early approval of their petition.
In the elections for Municipal leaders in 1919, the El ProgresoSalayano fields their own candidates for the presidency and vice-presidency of the Municipality of Balingasag of which Salay was part of. Also, they supported the candidacy of Mr. Jose Artadi for the post of Congressman of Misamis Oriental. All those whom the El ProgresoSalayano supported won during the elections. It was, however, Congressman-elect Jose Artadi who, late in 1919, brought the petition of the Salayano personally to the governor-general in Manila. The American governor-general promptly approved the petition. Salay thus became one of the first municipalities of Misamis Oriental and was inaugurated on January 1, 1920.