Idaho State Senate District 18

State Legislative District Profile (Upper Chamber)

Overview

District ID
id-sd-018
State
Idaho
Chamber
Upper chamber (state senate)
District Code
018
Land Area
139.5 sq mi
Water Area
3.65 sq mi

Boundary

Boundary of Idaho State Senate District 18

Boundary as GeoJSON

Source: U.S. Census Bureau TIGER/Line state legislative district boundaries.

Counties

CountyOverlapShare of district landShare of county land
Ada County139.48 sq mi100.0%13.3%

Showing all 1 county

Places

PlaceOverlapShare of district landShare of place land
Boise City city28.51 sq mi20.4%33.5%

Showing all 1 place

Overlapping Congressional Districts

Congressional districtPopulation in bothShare of this district's populationShare of the congressional district's populationShare of this district's land
ID District 247,20990.9%5.1%75.3%
ID District 14,7399.1%0.5%24.7%

Source: U.S. Census Bureau 2020 blocks and 2025 block equivalency files (119th Congress, 2024 state legislative plans).

Voters

Registered Voters
28,058
Active Voters
28,058 (100.0%)

Party Registration

PartyVotersShare
Democratic6,76224.1%
Republican11,14239.7%
Unaffiliated9,81635.0%
Other parties3381.2%
No party recorded00.0%

Turnout by Cycle

CycleGeneralDemocratic PrimaryRepublican Primary
2025–20268,275 (29.5%)0 (0.0%)0 (0.0%)
2023–202424,929 (88.8%)0 (0.0%)0 (0.0%)
2021–202217,687 (63.0%)0 (0.0%)0 (0.0%)
2019–202020,384 (72.6%)5,865 (20.9%)3,368 (12.0%)
2017–201815,480 (55.2%)1,886 (6.7%)3,220 (11.5%)
2015–201614,677 (52.3%)833 (3.0%)3,061 (10.9%)
2013–20149,866 (35.2%)642 (2.3%)1,700 (6.1%)
2011–201211,584 (41.3%)0 (0.0%)0 (0.0%)

Turnout counts today's registered voters with a counted ballot in the cycle's elections (the odd and even year), as a share of today's registered voters. Voters who have since left the rolls are not counted.

Browse the voter list for this district (premium access; sign-in required)

Source: Civitech voter file snapshot as of 01/12/2026. These are registered voters, separate from the Census population figures. Counts under 10 are suppressed and shown as "<10".

Demographics

Total Population
54,113 (± 1,858)
Median Age
35.9
Median Household Income
$100,140 (± $3,984)
High School Graduate or Higher (age 25+)
94.5%
Bachelor's Degree or Higher (age 25+)
51.1%

Population by Age

GroupPeopleShare
Under 187,90514.6%
18 to 6438,74471.6%
65 and over7,46413.8%

Population by Race and Hispanic Origin

GroupPeopleShare
Hispanic or Latino (any race)4,4138.2%
White, not Hispanic41,96577.6%
Black, not Hispanic9661.8%
Asian, not Hispanic3,3836.3%
American Indian / Alaska Native, not Hispanic4220.8%
Native Hawaiian / Pacific Islander, not Hispanic3890.7%
Some other race, not Hispanic4930.9%
Two or more races, not Hispanic2,0823.8%

Source: U.S. Census Bureau, American Community Survey 2020-2024 ACS 5-year estimates (tables B01001, B01002, B01003, B03002, B15003, B19013) for this state legislative district. Estimates are survey-based; ± figures are 90% margins of error.

Citizen Voting Age Population

Total Citizen Population
51,524
Citizen Voting Age Population (CVAP)
43,924

Citizen Population by Race/Ethnicity

GroupCitizensShare
Non-Hispanic47,39592.0%
Hispanic4,1308.0%
White42,45282.4%
Black7021.4%
Asian1,9433.8%
American Indian / Alaska Native4200.8%
Native Hawaiian / Pacific Islander3500.7%
Two or More Races1110.2%

Citizen Voting Age Population by Race/Ethnicity

GroupCVAPShare
Non-Hispanic40,59892.4%
Hispanic3,3247.6%
White37,07984.4%
Black6111.4%
Asian1,8704.3%
American Indian / Alaska Native7531.7%
Native Hawaiian / Pacific Islander2110.5%
Two or More Races750.2%

Source: Redistricting Data Hub / U.S. Census Bureau CVAP Special Tabulation (2020-2024 ACS 5-year).