How large, in acreage, was the fictional Ponderosa Ranch on the show Bonanza?

The Ponderosa was the fictional setting for Bonanza. According to the first episode ("Mr. Henry Comstock") filmed after the pilot, it was a thousand square miles (640,000 acre or 2,600 km2) ranch on the shores of Lake Tahoe, nestled high in the Sierra Nevada, with a large ranch house in the center of it. Ben Cartwright was said to have built the original, smaller homestead after moving from New Orleans with his pregnant third wife Marie and his two sons, Adam and Hoss. The grown Adam, an architect/engineer, designed the later sprawling ranch house as depicted on TV.