The Age of Congress

Ages

Ages are computed from each member’s date of birth, anchored at midnight Eastern Standard Time, using a mean Gregorian year of 365.2425 days. The clocks on this page advance in real time; nothing is estimated between updates.

Members

Averages cover voting members only: senators, and representatives of the fifty states. The 6 non-voting House members — the territorial delegates and the Resident Commissioner of Puerto Rico — are excluded from House averages. Vacant seats reduce the divisor rather than being imputed — figures are currently based on 100 sitting senators (of 100 seats) and 431 voting representatives (of 435 seats).

Party

“Across the Aisle” compares members by their current-term party. Party mean ages use the same edition-year age convention as the rest of the page. The average Democratic–Republican comparison is a Welch two-sample t-test, which does not assume the two parties’ age spreads are equal; the difference is well within what chance produces, so the two averages are treated as indistinguishable. The tail figures — how many members pass 65, 70, 75 and 80 — are plain counts, and because several thresholds were examined they are reported as counts rather than as significance tests. The 3 independents (Sanders and King in the Senate, and one representative) are shown on their own and are never folded into the party they caucus with.

Sources

Membership, birth dates, party, and term histories come from the @unitedstates congress-legislators dataset (CC0), maintained within days of congressional changes; this site rebuilds from it daily. The birth date of every member shown with a portrait — the oldest and youngest of each chamber — is additionally cross-checked against Wikidata at build time; the site does not publish if the two sources disagree.

History

Historical averages are computed from the same project’s records of the roughly 12,500 people who have served since 1789: for each Congress, the mean age of members serving on its constitutional first day (March 4 through the 73rd Congress, January 3 thereafter). Birth dates are unknown for 18% of the 2,585 people whose service ended before 1850 — those members are excluded and affected years are drawn lighter. From 1850 onward coverage never falls below 92.3% (the 32nd Congress, 1851); it is short of 99% in 8 of the 88 Congresses since. Values were validated against Congressional Research Service figures for recent Congresses and FiveThirtyEight’s member-level dataset (66th–118th Congresses). The chart’s U.S. line is the median age of adults 18 and older, 1980 to the present, derived from Census Bureau single-year-of-age estimates (five keyless published series) by linear interpolation; it is fixed history, derived once and committed, and each build checks its endpoint against the independently derived population baseline before publishing.

Arrivals

“Why It Stays Old” counts a person as a new House member exactly once, at the Congress where their earliest voting House term began — a returning member counts at their first arrival, a representative who becomes a senator does not count twice, and territorial delegates never count. Cohort ages are medians taken at the convening date. The series is recomputed from the rosters each build and validated against the published medians for 1979 (≈39) and the current Congress (≈50) before it can publish.

Districts

The map compares each representative against the people they represent. District age is the median age of adults 18 and older, derived from U.S. Census Bureau, 2024 American Community Survey 1-Year Estimates, table B01001 (Sex by Age), by interpolating across the published 18+ age brackets; the national figure on that basis is 47.5 years. Boundaries are the 119th-Congress districts, which match this roster seat for seat. The gap is the member’s age at the edition date minus that median, so it moves with the roster rather than with the reader’s clock. Of 435 districts, 431 have a sitting member and 4 are vacant; vacant seats are hatched, not shaded, because an empty seat has no age and is not a gap of zero.

Map

Districts are drawn from U.S. Census Bureau TIGER/Line cartographic boundaries for the 119th Congress, projected to Albers USA with Alaska and Hawaii inset. It is a real geographic map, so a physically small urban district reads small and a large rural one large; the color, not the area, carries the data. Public domain.

Birthdays

Birth dates come from the same @unitedstates congress-legislators dataset (CC0) as every other figure here, and the comparison covers voting members only — 531 of them, on the same basis as the averages above. The calendar carries all 366 dates a birthday can fall on; the roster currently occupies 261 of them and leaves 105 empty. The random baseline against which those are measured is the textbook uniform model, in which every birthday is equally likely and February 29 is ignored: n(n−1)/2 ÷ 365 expected sharing pairs, and 365 × (1 − 1/365)ⁿ expected days with nobody. Only birth years are shown by name; the section makes no claim about why the year is shaped the way it is.

Portraits

Portraits are official congressional photographs (public domain), courtesy of the U.S. Senate Historical Office and the Collection of the U.S. House of Representatives, via the @unitedstates images project.

Built by Annas Rahman · updated daily · generated 2026-07-23