Fairfield County

How This FIPS Code Works

Adjacent Counties (7)

Counties that share a border with Fairfield County. Useful for regional analysis — these are the geographies you'd typically include when studying labor markets, commuting zones, or environmental spillovers around FIPS 09001.

Federal Datasets Using Code 09001

FIPS code 09001 appears as the county identifier in the following federal datasets. Analysts joining data across these sources use this code as the common geographic key.

Using FIPS Code 09001 in Code

Common patterns for querying federal datasets by this county's FIPS code. The leading zeros are significant — always treat FIPS codes as strings, not integers.

import requests

url = "https://api.census.gov/data/2022/acs/acs5"
params = {
    "get":  "NAME,B19013_001E,B01003_001E",
    "for":  "county:001",
    "in":   "state:09",
    "key":  "YOUR_CENSUS_API_KEY",
}
r = requests.get(url, params=params)
data = r.json()  # [[header...], [Fairfield County, Connecticut, income, pop, ...]

-- 5-digit combined FIPS (state + county)
SELECT * FROM your_table WHERE county_fips = '09001';

-- Some datasets store state and county separately
SELECT * FROM your_table
WHERE state_fips = '09'
  AND county_fips = '001';

-- ⚠ Never cast to integer — leading zeros are lost:
-- county_fips = 9001 is WRONG for this county

library(tidycensus)

get_acs(
  geography = "county",
  variables = c(income = "B19013_001E", pop = "B01003_001E"),
  state     = "09",
  county    = "001",
  year      = 2022
)

ZIP Codes in Fairfield County

ZIP codes do not align perfectly with county boundaries — a single ZIP code can span multiple counties, and a county can contain parts of many ZIP codes. The ratios below (from the Census 2020 ZCTA relationship file) show the land area share of each ZCTA that falls within Fairfield County. Why FIPS ≠ ZIP →