The city is located on the southern bank of the Rio Grande in the international Reynosa–McAllen metropolitan area, directly across the Mexico–United States border from Hidalgo, Texas.

[4] On 6 July 1686, Agustín Echeverz y Zuvízar, governor of the Nuevo Reino de León, camped in what is now Reynosa during an exploratory expedition.

In December 1748, an expedition led by José de Escandón y Helguera left from Querétaro, planning to establish 14 villages; the caravan consisted of 1500 colonists and 755 soldiers.

The city was named Reynosa after Reinosa, birthplace of the viceroy Juan Francisco de Güemes y Horcasitas.

On 9 July 1757, arrives to the village the captain José Tineda y Cuervo and the engineer Agustín López, both viceroyalty inspectors, to do a population census according to which Reynosa had 280 inhabitants.

[5] As a result of the census, they obtained authorization from the King of Spain to move the village to a placed named Santa María de las Lajas, which was not done because Escandón didn't consider the river a flooding risk anymore.

[11] Reynosa is the largest and most populous city in the state of Tamaulipas, followed by Matamoros, Nuevo Laredo, Ciudad Victoria, Tampico, and Río Bravo.