The city of New Orleans has unveiled a smartphone app tour of sites involved in the slave trade during the 18th and 19th centuries, including the pre-Civil War years during which the city was the nation's largest slave market.

The project, officially launched on Thursday, is affiliated with New Orleans' tricentennial celebrations. It comes as cities around the country are shining an unblinking light on slavery and racial violence through such projects as a slavery museum outside New Orleans, an Alabama memorial to victims of lynchings, and the preservation of slave cemeteries.

In announcing the app at a news conference, African-American Mayor LaToya Cantrell said the New Orleans Slave Trade Marker and App Project "will let us honor the lives and dignity of those ancestors who were undoubtedly bought and sold here."