What was MOST responsible for Georgia’s expansive development in the late 1800s?

The most responsible factor for Georgia's expansive development in the late 1800s was the growth of the railroad industry. The introduction of railroads in Georgia allowed for the rapid transportation of goods and people, connecting the state to markets in other parts of the country and facilitating economic growth. The expansion of railroads also spurred the growth of industries such as agriculture, manufacturing, and mining, leading to increased prosperity and development in Georgia during this time period.