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Section lines in the United States are one mile (1.6 km) apart. When surveyors originally mapped an area, for instance a township, it was their custom to divide the new township into 36 1-square-mile sections (2.6 km2). Property ownership often followed this layout. A section is a 1-by-1-mile (1.6 km) area. A half section is a 1/2-mile by 1-mile area. It is proper to continue this division down to a 1/4-by-1/4 section which is 1/16 of a section, or 40 acres (16 ha). The next smaller division is 10 acres (4.0 ha), and then 2.5 acres (10,000 m2). Besides property ownership, roads called section line roads often followed the section lines, and one can often still see them in modern maps, even in urban areas. In rural areas, these roads are called section roads, and often exist primarily so that farmers can access their land.