In 1899, the United States Department of War conducted a census of Puerto Rico finding that the population of Hato Viejo barrio was 1,800.

The Manatí Bridge at Mata de Plátano, built in 1905, is located in Hato Viejo and is touted as a tourist site.

The legend says a mother who was working picking fruit had her son with her and that because he kept frolicking around her, she asked him to stay in the cave while she labored.

In her final attempt to have her son wait for her at the cave while she worked she sang him a song as she slowly walked away.

Locals say they hear a boy crying near the cave, and see him frolicking and when they try to catch him, he disappears, only to reappear again steps away.