"(...) Zwei Volksstämme, die sich nicht nur nach ihren Wohnsitzen, sondern auch nach ihren Sitten scheiden, bewohnen es; den nach Westen und Süden gelegenen Theil nehmen die Deutschen ein, den Theil nach Osten und Norden zu die Polenö beide trennt als eine ganz sichere Grenze die Oder von der Neißemündung ab, sodaß auch in den Städten diesseits die deutsche, jenseits die polnische Sprach vorherrscht. Man erkennt zwischen beiden Völkern einen starken Gegensatz. (...)"
In English:
"(...) It is inhabited by two nations, distinct from each other not only in terms of territories they occupy, but also in terms of customs; Western and Southern parts are inhabited by Germans, while Eastern and Northern parts are inhabited by Poles, both nations are divided by safe boundary along the Oder River starting from the outlet of the Neisse River in such a way, that also in cities on one side of the river we can hear German speech, while in cities on the other side by contrast we can hear Polish speech. Between these two nations there are strong differences. (...)"
Source:
Barthel Stein, "Descriptio Tocius Silesie et Civitatis Regie Vratislaviensis", published in 1513.
Please note that the city of Wrocław / Breslau was located on both sides of the Oder River.
Indeed, that part of Wrocław which was located on the eastern bank of the River, was called "Polnische Seite".
In fact detailed research shows that also some areas to the west of the Oder River were at that time mostly-Polish speaking.
On previous pages I posted a linguistic map of Silesia in ca. year 1650 (so already 137 years after Barthel Stein's description):
Blue = areas with German-speaking majority and red = areas with Polish-speaking majority (ca. year 1650):
http://postimg.org/image/k4134c499/full/
But at that time some areas to the east of the Oder River - especially in the north (as you can see) - were already Germanized. Regarding situation in the 1500s, it is described by Polish historians (for example: J. Kuczer's book on nobility in Duchy of Glogau in period 1526 - 1740, W. Dziewulski's study on population of Silesia in late 16th and early 17th centuries, A. Kowalska's article on Polish language in Silesia in period 1526 - 1742).
As well as:
T. Ładogórski, "Attempts of researching Polish-German linguistic border in Lower Silesia during the 1500s"
D. Dolański, "Poles and Germans in northern parts of Silesia during the 1500s"
Apart from Poles and Germans, in Silesia lived also Czechs, but their proportion compared to the other two groups was very small (A. Kowalska).
In the map I posted above, territories with Czech-speaking and Moravian-speaking majority in ca. year 1650 are marked with green colour.
- 1514 other people also declared themselves as Wielkopolans in 2011, including 380 as just Wielkopolans alone, 1109 as both Poles and Wielkopolans, and finally 26 declared themselves as Wielkopolans and something else (for example, Wielkopolanin-Niemiec).