5,408 people (2024 Census estimate, −0.5% since 2020)
1,028 square miles of land · 5 people per square mile
“Highest” and “lowest” are just order, not grades: a high rank for poverty or hazard losses means more of it. Each figure's source is in its section below.
10 active community water systems list Day County in the area they serve, reporting 32,197 people served in all (a system that crosses county lines counts its whole population).
| WEB WATER DEVELOPMENT ASSOCIATION surface water · private · SD4601089 | 20,750 served |
| BROWN-DAY-MARSHALL RWS groundwater · private · SD4600882 | 5,673 served |
| CLARK RURAL WATER SYSTEM groundwater · private · SD4600881 | 2,325 served |
| WEBSTER buys surface water · local government · SD4600360 | 1,728 served |
| CLARK RURAL WATER-KAMPESKA groundwater · private · SD4602277 | 602 served |
| WAUBAY groundwater · local government · SD4600357 | 473 served |
| BRISTOL buys surface water · local government · SD4600067 | 288 served |
| ROSLYN buys surface water · local government · SD4600284 | 181 served |
Source: U.S. EPA Safe Drinking Water Information System (SDWIS), active community systems, . Look up any system's violations and test results with EPA's search using its ID.
About 9 people were held in Day County's jail, in Vera's latest figure (2019), or 293 per 100,000 residents ages 15–64. In 2014 it was about 6.
Source: Vera Institute of Justice, Incarceration Trends (built from federal Bureau of Justice Statistics jail surveys). Counties without their own jail, or that share one, may show no figure.
2 school districts have their office in Day County. School taxes are usually the largest part of a property tax bill.
Spent $13 million — $6 million to run schools, about $10,853 per student, plus $6.6 million on buildings and equipment. Money in: $5.7 million local (mostly property tax), $1.4 million state, $1.4 million federal. Long-term debt: $11.4 million.
Spent $3.9 million — $2.8 million to run schools, about $15,137 per student, plus $1.2 million on buildings and equipment. Money in: $1.7 million local (mostly property tax), $835,000 state, $2.1 million federal.
Source: U.S. Census Bureau, 2023 Annual Survey of School System Finances. Districts are listed by the county of their main office; some serve neighboring counties too.
Source: County Health Rankings & Roadmaps 2025 (University of Wisconsin Population Health Institute), which gathers federal data (CDC, Census, and others); measures cover different recent years. Blank lines aren't reported for small counties.
Overall risk: Very Low compared with other U.S. counties. FEMA estimates natural hazards cost Day County about $7.2 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Very High; social vulnerability: Relatively High.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
34 bridges in Day County: 15 in good condition, 10 fair, and 9 poor (26.5%). “Poor” means a main part — the deck, the beams, or the supports — is rated 4 or lower on the federal 0–9 scale. It doesn't mean unsafe to drive; unsafe bridges are closed.
| 425TH AVENUE over BURLINGTON NORTHERN RR · built 1960 | 274 vehicles a day |
| 423RD AVENUE over BURLINGTON NORTHERN RR · built 1938 | 218 vehicles a day |
| 137TH STREET over CREEK · built 1926 | 115 vehicles a day |
| 12590-416TH AVENUE over CK · built 1932 | 70 vehicles a day |
| 412TH AVENUE over CREEK · built 1920 | 69 vehicles a day |
| 127TH STREET over CREEK · built 1930 | 15 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $13.8 million of work in Day County in fiscal 2025, about $2,525 per resident — to the county, cities, schools, hospitals, nonprofits and others.
Source: USAspending.gov, grants by place of performance, fiscal 2025 (Oct. 2024 to Sept. 2025). Search it by county to see each award.
From Grants.gov: posted grants listing county governments as eligible, soonest deadline first; research-only and overseas programs left out; list updated 2026-10-13, refreshed weekly. 62 are open in all. Cities, towns, school districts and nonprofits have their own lists there.
Registration deadlines, early voting and polling places for South Dakota are on the federal site vote.gov, which links to the state's official election office.
The budget, property tax rates, audits, local officials and offices for Day County come from the county's own records, which we haven't gathered — not gathered, never hidden. See what a full county site looks like, or ask to have Day County built: brayden.ozark@gmail.com.
More of South Dakota: the state government and every county in South Dakota.
Nearby counties: Marshall County (26 mi) · Codington County (33 mi) · Clark County (35 mi) · Roberts County (36 mi) · Brown County (41 mi) · Grant County (41 mi).