ZIP code 21104: Eldersburg, MD
ZIP code 21104 is in Eldersburg (43% of residents) and Ellicott City (19%), in Howard County (54%), Carroll County (43%) and Baltimore County (2.7%), Maryland. 38% of its residents live outside city limits. It is in Maryland's 3rd congressional district (54%) and Maryland's 2nd congressional district (46%). Its state senate districts are State Senate District 9 (54%), State Senate District 5 (43%) and State Senate District 10 (2.7%); its state house districts are State Legislative Subdistrict 9A (54%), State Legislative District 5 (43%) and State Legislative District 10 (2.7%).
See it on the mapAll of Maryland
City and county
| City or town | Share of ZIP residents |
|---|---|
| Eldersburg | 43% |
| Ellicott City | 19% |
| County | Share of ZIP residents |
|---|---|
| Howard County | 54% |
| Carroll County | 43% |
| Baltimore County | 2.7% |
| Town or county subdivision | Share of ZIP residents |
|---|---|
| District 3, West Friendship | 54% |
| District 5, Freedom | 43% |
| District 2 | 2.7% |
Congressional districts
| Congressional district | Share of ZIP residents |
|---|---|
| Maryland's 3rd congressional district (MD-03) | 54% |
| Maryland's 2nd congressional district (MD-02) | 46% |
This ZIP is split between districts. A mailing address in it could be in either; the map or locate_point gives the district for an exact address.
Elected officials
| Office | Member | Contact | Share of residents |
|---|---|---|---|
| U.S. Representative (MD-03) | Sarah Elfreth (D) | 202-225-4016 | 54% |
| U.S. Representative (MD-02) | Johnny Olszewski, Jr. (D) | 202-225-3061 | 46% |
| U.S. Senator | Angela D. Alsobrooks (D) | 202-224-4524 · contact form | statewide |
| U.S. Senator | Chris Van Hollen (D) | 202-224-4654 · contact form | statewide |
| State Senator (State Senate District 9) | Katie Hester (Democratic) | 54% | |
| State Senator (State Senate District 5) | Justin Ready (R) | 43% | |
| State Senator (State Senate District 10) | Ben Brooks (Democratic) | 2.7% | |
| Delegate (State Legislative Subdistrict 9A) | Chao Wu (Democratic) | 54% | |
| Delegate (State Legislative Subdistrict 9A) | Natalie Ziegler (Democratic) | 54% | |
| Delegate (State Legislative District 5) | April Rose (R) | 43% | |
| Delegate (State Legislative District 5) | Chris Tomlinson (R) | 43% | |
| Delegate (State Legislative District 5) | Christopher Bouchat (R) | 43% | |
| Delegate (State Legislative District 10) | Adrienne Jones (Democratic) | 410-455-5330 | 2.7% |
| Delegate (State Legislative District 10) | Jennifer White Holland (Democratic) | 2.7% | |
| Delegate (State Legislative District 10) | Scott Phillips (Democratic) | 2.7% |
Officials serving now (members of Congress until January 3, 2027). Sources: State legislators: Open States (public domain); Members of Congress: the @unitedstates project, congress-legislators (CC0).
Local government
- Eldersburg laws: search for the Eldersburg, Maryland code of ordinances
- Ellicott City laws: search for the Ellicott City, Maryland code of ordinances
- Howard County website: https://www.howardcountymd.gov/
- Howard County laws: search for the Howard County, Maryland code of ordinances
- Carroll County website: https://www.carrollcountymd.gov/
- Carroll County laws: search for the Carroll County, Maryland code of ordinances
State legislative districts
| State senate district | Share of ZIP residents |
|---|---|
| State Senate District 9 | 54% |
| State Senate District 5 | 43% |
| State Senate District 10 | 2.7% |
| State house district | Share of ZIP residents |
|---|---|
| State Legislative Subdistrict 9A | 54% |
| State Legislative District 5 | 43% |
| State Legislative District 10 | 2.7% |
Voting precincts
6 voting precincts overlap ZIP 21104. Map them, with each precinct's share of the ZIP's residents.
Get this in your AI agent
Your agent can get these cities, counties, districts and precincts with their shares, and their GeoJSON boundaries, from Boundary Atlas. Add https://atlas-production-d344.up.railway.app/mcp to Claude, ChatGPT, Cursor or Codex (free, no key; how), then:
related_geographies(id="us:zcta:21104")
ZIP 21104 here is the Census Bureau's ZIP Code Tabulation Area, which approximates the USPS ZIP Code; PO-box-only ZIPs have none. Districts are the maps in force for the November 3, 2026 election.