Complex sentence: The earliest significant settlement of the district does not appear to have taken place until the mid or late 1840's an 1851 map of this area indicate4s that one a dozen scattered houses and shops were standing in the area by that time.
Split into simpler sentences: The earliest significant settlement of the district does not appear to have taken place until the mid or late 1840s. An 1851 map shows that only about a dozen scattered houses and shops were standing in the area by that time.