For 130 years, Chicago and New York City have been locked in a battle of the skyscrapers. Nine of the tallest buildings in the U.S., as well as more than one-half of the nation's towers greater than 785 feet, were built in just those two cities.

Retailers are already planning for the busy holiday shopping season, and there could be a complication this year. As the unemployment rate drops, stores are having a hard time finding workers for their warehouses. They've ordered all kinds of new stuff for the holidays, but it's stuck in a bottleneck.

Are robots taking over the warehouse?