Wall Street's main indexes fell on Thursday as investors awaited monetary policy clues from the Federal Reserve's annual economic symposium, while big-box retailer Walmart's quarterly results dampened sentiment.

Wall Street closed lower on Thursday, pressured by declining shares of Walmart (WMT) all while investors look ahead to Federal Reserve Chair Jerome Powell’s upcoming speech at Jackson Hole on Friday.

The investing world will turn its attention to northwestern Wyoming in the week ahead, with Federal Reserve Chair Jerome Powell set to give his most important policy speech of the year on Friday at the annual Jackson Hole Economic Symposium.