Exhibit 99.1 KIRBY CORPORATION Contact: Kurt Niemietz 713-435-1077 FOR IMMEDIATE RELEASE KIRBY CORPORATION ANNOUNCES 2024 FIRST QUARTER RESULTS • First quarter 2024 earnings per share of $1.19 • Inland marine experienced strong market conditions with a sequential increase in spot market prices and high-teens operating margins despite a sequential increase in delay days • Coastal operating margins improved to high single to low double-digit range • Breaking out power generation at KDS as its significance con ...