[11][12] For the 2020 U.S. Census, the boundary was redrawn so that portions of Lower Township were included in the Rio Grande CDP.

[15] According to Jeffrey M. Dorwart, Rio Grande was founded in the mid-nineteenth century around a country store owned by the Hildreth family.

[16] George F. Boyer and J. Pearson Cunningham explain that, during the colonial period, Aaron Leaming, the Hildreths and the Cresses had plantations in that area.

Where the King's Highway crossed the road coming from Dennisville and Goshen a stage coach terminal was set up, and the spot became the center for trade for the local farming families.

Boyer and Cunningham say that the area was known as "Leamings," for the prominent landholders, or as "Hildreth," the family who ran the local store.

(p. 121-122) They continue, "The name, Rio Grande, was suggested by the seventh Aaron Leaming who thought this southern United States river had an attractive sound.

[18][19] The climate in this area is characterized by hot, humid summers and generally mild to cool winters.

[20] The 2010 United States census counted 2,670 people, 1,115 households, and 730 families in the CDP.

In the era of de jure educational segregation in the United States, a school for white children in grades 1-6 was maintained in Rio Grande and a school for black children was maintained in Whitesboro in grades 1–8.

White children in Rio Grande were sent to West Cape May School District for grades 7–12.

[28] Cape May Airport, established in 1941 as NAS Rio Grande, is located in the area,[10] in adjacent Lower Township.