Castine was platted in 1832 and replatted in the following year. Its location was chosen because it lay at the intersection of the road between Greenville and Eaton with the road between the communities of Miami County, Ohioand New Garden, Indiana. For its first few decades, the village (then known as “New Castine”) grew and prospered, but the building of the Little Miami Railroad through West Manchester, just 2 miles (3.2 km) to the south, retarded Castine’s progress. Revival came with the construction of the Cincinnati Northern Railroad in 1894.
According to the United States Census Bureau, the village has a total area of 0.08 square miles (0.21 km2), all of it land.
As of the census of 2010, there were 130 people, 54 households, and 36 families residing in the village. The population density was 1,625.0 inhabitants per square mile (627.4 /km2). There were 59 housing units at an average density of 737.5 per square mile (284.8 /km2). The racial makeup of the village was 97.7% White, 0.8% Native American, 0.8% from other races, and 0.8% from two or more races.
There were 54 households of which 29.6% had children under the age of 18 living with them, 53.7% were married couples living together, 7.4% had a female householder with no husband present, 5.6% had a male householder with no wife present, and 33.3% were non-families. 31.5% of all households were made up of individuals and 18.5% had someone living alone who was 65 years of age or older. The average household size was 2.41 and the average family size was 2.97.
The median age in the village was 35.5 years. 23.8% of residents were under the age of 18; 5.5% were between the ages of 18 and 24; 31.6% were from 25 to 44; 23.1% were from 45 to 64; and 16.2% were 65 years of age or older. The gender makeup of the village was 49.2% male and 50.8% female.