Complex sentence: In 1801 Birkenhead was still a small, undeveloped village on the banks of the River Mersey with a recorded population of 110, it was overshadowed by the huge maritime port of Liverpool.
Split into simpler sentences: In 1801 Birkenhead was still a small, undeveloped village on the banks of the River Mersey. With a recorded population of 110, it was overshadowed by the huge maritime port of Liverpool.