State · 1138 – 1526

Duchy of Masovia

A state of 1138 – 1526 — 388 years in Europe. The atlas records 1 thing within it — people 1. Its line of rulers holds 7 people. Its own article says it was conquered by Kingdom of Poland.

For the full story, the article on Wikipedia (CC BY-SA 4.0); this page holds what the record says of the state.

Stood: 388 years; 1138 – 1526
Rulers: 7; the Duke of Masovia
Most ground: 165,800 km²; in 1147
Within it: 1; recorded row
Symbols: 2; on record, with years

Map: Duchy of Masovia in 1147, its borders in gold among its neighbours — Duchy of Masovia in 1147, when it held the most ground the borders dataset draws for it: 165,800 km². Its neighbours wear their tints, as on the atlas's own map. Borders from Cliopatria (CC BY 4.0), coast and rivers from Natural Earth, cities from Reba, Reitsma & Seto 2016 (CC BY 4.0), each city under the name it bore that year.

Duchy of Masovia in 1147, at its largest — The rise and the fall in one frame: the same ground at the years the borders dataset first maps it, maps it largest, and last maps it.

Duchy of Masovia in 1344, last mapped — The rise and the fall in one frame: the same ground at the years the borders dataset first maps it, maps it largest, and last maps it.

Where it sits in time

Five thousand years, 3000 BCE to 2026; the state in gold.

How it ended, as its article says

Conquered by Kingdom of Poland, 1526. Read from the article's section “lead” by its grammar; the claim is only that the article says so.

In 1526, the country was incorporated into the Kingdom of Poland.

One sentence of the English Wikipedia article, CC BY-SA 4.0.

Rulers

Read from the state’s own English article and its rulers’ articles, where Wikidata names no ruler.

ending not on recorda second row: a reign that began before the last had ended — rival claimants, or a shared throne

Ruler	Reign	Length	How it ended · source	To the ruler before
Bolesław IV the Curly	1138 – 1138	under a year	ending not on record
Leszek, Duke of Masovia	1173 – 1186	13 years	ending not on record	child
Casimir II the Just	1186 – 1194	8 years	ending not on record
Leszek I the White	1194 – 1200	6 years	ending not on record	child
Konrad I of Masovia	1194 – 1247	53 years	ending not on record	sibling
Siemowit I of Masovia	1248 – 1262	14 years	ending not on record	child
Janusz III of Masovia	1503 – 1503	under a year	ending not on record

7 rulers, 7 with terms dated as terms, covering 1138 – 1503. Median reign 8 years. 1 of 6 handovers irregular - a killing, a deposition, a rival claimant, a rising or a coup beside it. A blank in the last column means no kin on record, which is coverage, never “unrelated”.

Ground held, by year

km² inside its borders as the borders dataset draws them, measured on an equal-area grid; a step series, held between the years the dataset maps.

165,800 km² in 1163, 25,800 km² in 1338; at its largest 165,800 km² in 1163. Cliopatria, CC BY 4.0.

Flags and arms, in order

Each symbol with the years its own statement gives; the timeline flies the one of the year on screen.

coat of arms, undatedKsięstwo Mazowieckie COA · CC BY-SA 2.5 · Poznaniak , smok Bastian
flag, undatedChorągiew Mazowsza · CC BY-SA 2.5 · Poznaniak , smok Bastian

What happened within it, by century

Every row the atlas hosts under this state, by the century it began in: wars and battles in red, risings, regime changes and massacres beside them, everything else in grey. A tall bar is a century the record is full for, which is partly a fact about Wikipedia.

1100 – 11991 row

Henry the Bearded · ruler · 1165 – 1238

Among all states

Each measure against the states that carry it, never against all of them: a bar is the share of those states below this one.

How long it stood388 years
stood longer than 80% of 3,187 states with a recorded end or still standing.
The most ground it held165,800 km²
held more ground at its peak than 55% of 1,465 states with a border in Cliopatria.
Wars recorded per centurynone
had more wars on record per century than 44% of 3,187 states, counting the wars the atlas hosts under each.
How long a reign lasted, at the median8 years
had longer reigns, at the median, than 29% of 967 states whose dated line can carry a median.
Rulers on record7
has more rulers on record than 73% of 1,968 states with a line of rulers.

Open in the atlas

On the timeline, 1099 – 1565, with everything that stood beside it.
On the map in 1147, live: scrub the year and watch its borders move.
Investigate it: what led to it, what came of it, and its succession analysed.

Wikidata Q2361927 (CC0) · borders Cliopatria, CC BY 4.0 · coast and rivers Natural Earth · symbols from Wikimedia Commons, each credited above · one sentence of the English Wikipedia article, CC BY-SA 4.0 · data built 2026-10-06 · Pastlas v2.9.1, by Oleh Voronko. The published atlas and its data are for non-commercial use.