Result of Polish presidential elections, May 2015, per region. Red line shows historical partition line | POLITICO/Data: Krajowe Biuro Wyborcze Poland’s past marks its present Poland’s presidential election again showed the profound differences between the east and the west.

WARSAW — Andrzej Duda’s victory over Bronisław Komorowski in Poland’s presidential election split the country along some old lines.

A glance at the results of last week’s vote in the map above shows that the center and east of the country went for Duda, while a majority of the west and the north opted for Komorowski. The demarcation between the two almost exactly follows the partition line that marked the border between the Russian, German and (in the southeast corner of today's Poland) Austrian-Hungarian empires — which existed from 1815 to 1918 — before World War I when the country was partitioned.

The divisions seen in the Komorowski-Duda contest have been visible in just about every past Polish election. Here below you see the previous two presidential polls. In 2010, the centrist Komorowski defeated Jarosław Kaczyński, the leader of the right-wing Law and Justice Party (PiS), by six percentage points. PiS got its man Duda over the finish line first last month. In the 2005 contest Jarosław's twin brother Lech Kaczyński, who died in a plane crash in 2010, defeated Donald Tusk by eight percentage points.

To the non-Pole, there is little to differentiate the two halves of the country. A mid-sized city like Biała Podlaska, lying not far from the border with Belarus, doesn’t seem all that different from Słupsk, just a few kilometers from the Baltic Sea. Both have a mix of older buildings and communist-era apartment blocks scattered across a largely flat countryside; the cars parked on sidewalks, wild profusion of billboards and dysfunctional urban planning are common across the country.

But scratch deeper and differences appear.

First, the politics. In the region around Biała Podlaska, Duda took 67 percent of the vote while Komorowski got only 33 percent. In Słupsk, Komorowski won 60 percent to Duda’s 40 percent. Local governments are different too. Słupsk is run by Robert Biedroń, Poland’s only openly gay mayor, while Biała Podlaska’s mayor is from the same right-wing Law and Justice party as Duda.

The broader region around Słupsk is much richer too. There, GDP per capita is 65 percent of the EU average, according to Eurostat, while the region around Biała Podlaska is one of Europe’s poorest at 48 percent.

Even the attendance at mass is different. Those in the east are likelier to go to church on Sunday than people in the west.

History offers an answer. When Poland lost its independence in the late 18th century to its three neighbors, a big chunk of the country ended up under Moscow’s control. The Russian empire underinvested in roads and railways, the Austrians did a little better but the Germans were the keenest builders. The Germans had taken over the most advanced and most Europeanized parts of pre-partition Poland, while the Russians took the poorest and least urban.

The three empires were then dissimilar in how they treated their pieces of Poland, differing in everything from bureaucracy to urbanization and school systems. Almost a century after Poland regained its freedom in 1918, those differences still matter.

The crucial one is that in most of the east, today’s people are descendants of those who lived in the area for centuries. Enduring family and local ties makes for a more conservative society. The region along the Baltic was only given to Poland after 1945, when most of the prewar German population was evicted. They were replaced by refugees, many fleeing from the east of prewar Poland which had been handed to the Soviet Union. Torn from their roots, the new population ended up being more cosmopolitan and politically more centrist than their cousins in the east. Even three generations later, the echoes of that post-war migration can still be heard.

The differences between regions can be overdone; Duda did get support in the west and Komorowski in the east. But just as with the enduring division between east and west Germany or northern and southern Italy, Poland’s past has left its mark on the present.