Understanding the Surveyor's "Perch": Historical Measurement Units

What Is a Perch in Land Surveying?

A "perch" (also "rod" or "pole") is a historical unit of length equal to 16.5 feet (5.5 yards). It was the fundamental measure in English and early American land surveys.

Hierarchy of Units

• 1 perch = 16.5 feet
• 4 perches = 1 chain = 66 feet
• 10 chains = 1 furlong = 660 feet
• 8 furlongs = 1 mile
• 1 acre = 10 square chains (66 ft × 660 ft)

Historical Context

• Standardized by Parliament in 1593; adopted by U.S. Congress in 1796 for the Public Land Survey System.
• Gunter's chain (66 ft, 100 links) became the standard surveyor's tool.
• Early chains had leather joints that stretched, causing measurement drift—hence irregular block sizes in cities like Santa Barbara.

Modern Relevance

Deeds and plats in older areas (original 13 colonies, Kentucky, Tennessee, Texas) may reference perches, rods, or chains. Surveyors still convert these to feet for retracement.

Conversion Reference

sizes.com/units/perch.htm provides detailed history and conversion tables.

Fun fact: Three of four Mount Rushmore presidents (Washington, Jefferson, Lincoln) were surveyors—perhaps explaining the monument's precision!