サウスダコタ州デューイ郡

• ファイアスティール・ダム州立狩猟生産地域
• イザベル湖州立狩猟生産地域
• リトル・モロー州立狩猟生産地域
• リトル・モロー州立レクリエーションエリア

• イザベル湖
• オアヘ湖（一部）
• リトル・モロー湖

2020年の国勢調査によると、同郡の人口は5,239人、世帯数は1,705、家族数は1,180で、人口密度は1平方マイルあたり2.3人（0.89/km ² ）であった。^{[ 13 ] [ 14 ]}

住民のうち、31.4%が18歳未満、12.0%が65歳以上で、年齢の中央値は32.4歳でした。女性100人に対して男性は100.0人で、18歳以上の女性100人に対して男性は97.6人でした。^{[ 13 ]}

同郡の人種構成は、白人16.3%、黒人またはアフリカ系アメリカ人0.2% 、アメリカ先住民およびアラスカ先住民78.9%、アジア人0.1% 、その他の人種0.3%、2つ以上の人種4.2%であった。ヒスパニックまたはラテン系の住民は、人種を問わず人口の1.5%を占めた。^{[ 14 ]}

郡内には1,705世帯があり、そのうち42.9%は18歳未満の子供が同居しており、31.8%は配偶者やパートナーのいない女性世帯主の世帯でした。全世帯の約24.9%は単身世帯で、8.6%は65歳以上の単身世帯でした。^{[ 13 ]}

住宅戸数は1,923戸で、そのうち11.3%が空室だった。居住中の住宅戸のうち、58.4%が持ち家、41.6%が賃貸だった。持ち家の空室率は0.3%、賃貸の空室率は10.3%だった。^{[ 13 ]}

As of the 2010 census, there were 5,301 people, 1,730 households, and 1,239 families in the county. The population density was 2.3 inhabitants per square mile (0.89/km²). There were 2,002 housing units at an average density of 0.9 units per square mile (0.35 units/km²). The racial makeup of the county was 74.9% Native American, 21.0% white, 0.2% Asian, 0.1% black or African American, 0.2% from other races, and 3.6% from two or more races. Those of Hispanic or Latino origin made up 1.8% of the population. In terms of ancestry, 13.2% were German, 6.5% were Irish, and 0.6% were American.

Of the 1,730 households, 45.9% had children under the age of 18 living with them, 37.6% were married couples living together, 24.2% had a female householder with no husband present, 28.4% were non-families, and 24.6% of all households were made up of individuals. The average household size was 3.05 and the average family size was 3.60. The median age was 30.0 years.

The median income for a household in the county was $33,255 and the median income for a family was $40,500. Males had a median income of $33,942 versus $28,594 for females. The per capita income for the county was $15,632. About 20.5% of families and 30.5% of the population were below the poverty line, including 39.5% of those under age 18 and 13.5% of those age 65 or over.

• Eagle Butte (partial)
• Timber Lake (county seat)

• Isabel

The county is divided into two areas of unorganized territory: North Dewey and South Dewey.