Amazon is expanding its same-day grocery delivery service to 1,000 cities and towns across the U.S., the company said Wednesday.

Amazon has positioned itself as America's most prominent shopping retailer, and a large part of that dominance is the two-day shipping offered for most items on the site. Customers with Amazon Prime are able to have items to their door within 48 hours of ordering,

Amazon is now offering shoppers in more than 1,000 cities free, same-day delivery of groceries --- including perishable goods.