ZIP Code 91730 · Rancho Cucamonga, California
San Bernardino County · 25,678 counted · 4 districts
Each percentage here is a share of the 25,678 homes counted in ZIP Code 91730, not the chance that any one address is in that district. Enrollment follows the street: two houses on opposite sides of the same road can be in different districts, and only the district office can say which.
The districts named for the early grades in ZIP Code 91730, Rancho Cucamonga, California are not the districts named for high school, and the set changes in both directions: one district arrives for high school that no elementary answer names, and another runs the early grades and stops. 4 districts hold the 25,678 homes counted here between them, and Central Elementary is the largest by homes. The largest share is high enough that one name is right for most of the homes counted and wrong for the other 0: 10,607 homes with Cucamonga Elementary and Etiwanda Elementary.
Three districts share the early grades
3 districts hold a measurable share of ZIP Code 91730 at this level. Central Elementary is the largest with 15,071 homes; the smallest of them holds 3,431 homes. Central Elementary, Cucamonga Elementary and Etiwanda Elementary are named here for grade school and not for high school.
Every track below is 35 cells long and stands for all 25,678 homes counted in ZIP Code 91730, so one cell is 734 homes, rounded to the nearest whole cell. Cells lit solid are the homes one district holds, and the unlit cells are the homes held by the other districts in the same list.
- Central Elementary School District15,071 of 25,678 homes59%
- Cucamonga Elementary School District7,176 of 25,678 homes28%
- Etiwanda Elementary School District3,431 of 25,678 homes13%
One district covers high school
Chaffey Joint Union High School District is the only high school district named for ZIP Code 91730 at all, and it holds 25,678 of the 25,678 homes counted in the area. Chaffey Joint Union High is named here for high school and not for the early grades.
- Chaffey Joint Union High School District25,678 of 25,678 homes100%
The set of names changes in both directions
Chaffey Joint Union High is named for high school here and for no elementary grades, and Central Elementary, Etiwanda Elementary and Cucamonga Elementary run the early grades and no more. An address on the wrong street can therefore change district at the change of grade and land in a district that was never part of its elementary answer, while a neighbor two blocks away keeps one name the whole way through.
What one district name costs in 91730
A lookup that answers ZIP Code 91730 with one district name has to pick one of the names below and drop the rest. Measured against the 25,678 homes counted here, for the early grades it is wrong for 10,607 homes and for high school one name is right for every home counted. That is the whole difference between this page and a one-line answer: the same federal file, read to the end instead of to the first row.
The districts that reach into 91730
The districts named above are not alike in size or in reach. Chaffey Joint Union High touches 18 ZIP Code areas in all and holds 25,678 homes inside this one; Central Elementary touches 2 areas. Not one of them is ever the only district in a ZIP Code area anywhere in the country: every postal area they touch, they share with somebody.
- Chaffey Joint Union High School District25,678 of 25,678 here · 18 ZIP areas in all
- Central Elementary School District15,071 of 25,678 here · 2 ZIP areas in all
- Cucamonga Elementary School District7,176 of 25,678 here · 6 ZIP areas in all
- Etiwanda Elementary School District3,431 of 25,678 here · 6 ZIP areas in all
Where Central Elementary goes from here
Central Elementary School District runs kindergarten through grade 8, and it is the only school district serving 0 of the 2 ZIP Code areas it touches, and shares the other 2 with neighbors. Inside its own boundary it holds 15,266 homes over 6 square miles; the part of it counted in ZIP Code 91730 is 15,071 of those. The district it shares the most postal ground with is Chaffey Joint Union High School District, across 2 ZIP Code areas. Its thinnest measured foothold is elsewhere: in ZIP Code area 91786 it holds 195 of 20,352 homes, or 1.0% of them.
How 91730 compares in California
Across California the boundary file names more than one district in 996 of the 1,788 ZIP Code areas it names a district for, 56% of them, and 3 areas in the state have no high school district named for part of their homes. Counting the districts named at either level, 150 areas in California name more than this ZIP Code does and 1,489 name fewer. Nationally more than one district is named in 53% of 33,555 areas.
Look up 91730 again, or look up another ZIP Code
The lookup holds every ZIP Code area in the country with homes in it, including the ones with no page of their own. Opening it at 91730 recomputes the same 25,678 homes from the same snapshot, and typing five other digits answers for somewhere else. Nothing here is fetched from anywhere while you read: the whole index travels with the lookup page itself.
What to do next
Ask the district office to confirm your street address. A district settles that question on its own site: look for a school locator, a find my school tool, or an attendance zone map. Where there is none, ask the office itself.
A ZIP Code is a set of mail delivery routes, not a boundary: one district covers every home counted in 91730, and even then the street is what enrolls a child, because magnet, charter and choice programs ignore the boundary entirely.
This site links to no district website. None of the federal files it is built from publishes one, and a guessed address is worse than none. It is the district office, not a search engine, that settles an address.
What this site can hand you instead:
If a house purchase depends on the answer, ask the district itself for written confirmation of that exact address. A listing is not a district record, and neither is this page.
What this cannot tell you
The homes were counted in the 2020 Census and the district lines are the 2026 boundary file. Nothing on this page adjusts one to the other. Where houses have been built or cleared since the count, a share here describes the place as it was counted rather than as it stands today, and in the fastest-growing ZIP Code areas that gap is the largest single source of error on this site.
A share on this page is a share of the homes in the ZIP Code area, not a probability for any particular address. Enrollment is decided by street address, and a district may run magnet, charter or choice programs that ignore the boundary entirely. If a decision depends on the answer, the district office is the only authority; this page shows what the federal boundary files say and when they were published.
A district boundary is not a school attendance zone. This site never says which school an address is assigned to: no current national dataset of attendance zones exists, and the district draws them itself. Nor is anything here endorsed or certified by the Census Bureau; we use their published files, and that is the whole of the relationship.
A ZIP Code is a set of mail delivery routes, not an area. What is mapped here is the Census Bureau's ZIP Code Tabulation Area, the closest published approximation to it. The two are not identical, and a handful of ZIP Codes used only for post office boxes or single buildings have no tabulation area at all.
Where these numbers come from
School district boundaries come from the Census Bureau's Census Geographic Relationship File, current 2026 vintage, which assigns every census block to a unified district or to an elementary and a secondary district. Homes and residents in each block come from the 2020 Census Redistricting Data (PL 94-171), H1_001 and P1_001. The ZIP Code areas come from the same Geographic Relationship File, block to ZIP Code Tabulation Area. District names and grade ranges come from the Census Gazetteer 2025, with 2020 for districts no longer listed.
The place name printed beside a ZIP Code comes from the Census 2020 ZIP Code Tabulation Area relationship files: place, county subdivision and county, taken 2026-09-06. It is a label rather than a measurement: the Census Bureau does not publish which post office a ZIP Code belongs to, so the place named is the one covering the most land inside the area, not the city the Postal Service prints on an envelope.
Everything else on this page — the shares, the counts of districts per ZIP, the comparison between the two grade bands, the rankings — is computed here from those files. The source publishes none of it. Snapshot taken 2026-09-03.