Castlewood, South Dakota Demographics & Population 2026

A note before these figures: with a population of 804, Castlewood's ACS estimates come from a small number of survey responses and carry wide margins of error. Individual percentages below — particularly rates that round to 0% or 100% — are approximations, not precise measurements. See data.census.gov for the published margins of error.

Population Overview

Castlewood is a small community located in South Dakota, within Hamlin County. The total population is 804. It ranks as the 101st most populous out of 439 Census-designated places in South Dakota.

Age Demographics

The median age in Castlewood is 36.5 years. This is 4% lower than the state median of 38.0 years. With 33.0% of the population under 18, Castlewood has a notably young demographic profile, suggesting a family-oriented community.

Economy, Income & Housing

The median household income in Castlewood is $87,045. This is 16% higher than the state median of $75,081. It is also 8% higher than the national median of $80,734. The poverty rate stands at 4.3%. This is 64% lower than the state poverty rate of 11.9%. This exceptionally low poverty rate indicates strong economic prosperity across the community. The unemployment rate is 1.8%. This is 40% lower than the state rate of 2.9%. The median home value is $198,200. Housing costs are 23% lower than the state median of $257,400. With a home-value-to-income ratio of just 2.3x, Castlewood is one of the most affordable housing markets in the area. 82.5% of occupied housing units are owner-occupied. This homeownership rate is 20% higher than the state average of 68.6%.

Race & Ethnicity

Castlewood has a predominantly White (non-Hispanic) population, comprising 90.8% of all residents. Black or African American residents account for 0.6%. The Black or African American population (0.6%) is well below the state average of 2.1%. The Hispanic or Latino population (0.5%) is well below the state average of 4.8%.

Education

24.9% of residents aged 25 and older hold a bachelor's degree or higher. This is 22% lower than the state rate of 31.9%. Nationally, 35.7% of adults hold at least a bachelor's degree. The high school graduation rate (or equivalent) is 98.4%.

Data Sources & Methodology

All demographic data for Castlewood, South Dakota is sourced from the U.S. Census Bureau's American Community Survey (ACS) 2020–2024 5-Year Estimates. The ACS collects data from approximately 3.5 million households annually and pools five years of responses so that even small communities can be measured, though the margin of error widens as the population falls. Comparisons are made against South Dakota state averages and national averages calculated from the same dataset. Rankings reflect the city's position among all 439 Census-designated places in South Dakota. Read more about how these figures are produced on our methodology page, or visit data.census.gov for official data.