Black Friday, the biggest shopping day of the year and the traditional start of the holiday shopping season, drew more crowds and generated more sales than ever before, according to Chicago-based research firm ShopperTrak.

Retail sales on Nov. 25 increased 6.6% compared to Black Friday in 2010, according to the ShopperTrak National Retail Sales Estimate. The total sales amount was $11.40 billion in retail purchases -- the highest figure on record, according to ShopperTrak. Retail foot-traffic rose accordingly, up 5.1% over the same day last year.

"This is the largest year-over-year gain in ShopperTrak's National Retail Sales Estimate for Black Friday since the 8.3% increase we saw between 2007 and 2006," said ShopperTrak founder Bill Martin. "Still, it's just one day. It remains to be seen whether consumers will sustain this behavior through the holiday shopping season."