The County's system of tax maps is based on the Illinois Public Land Survey System (PLSS). In the PLSS, each township is divided into 36 sections, and each section into four quarter-sections. A quarter-section is further divided into two tax map sheets, often called "pages". Each tax map (1/4 mile by 1/2 mile) represents the east or west half of one quarter-section, and typically there are eight tax maps per section.