Rice is among the top seven U.S. major crops in terms of harvested acres – covering over 2.6 million acres – and sixth in terms of sales, with annual cash receipts around 3.1 billion dollars. This paper investigates whether U.S. milled rice markets are integrated across regions and whether these markets are integrated by rice types. Understanding dynamic relationships across regions and types provides important insights for risk management and policy making. Of the four major producing regions, three are in the South – Arkansas-Missouri, Louisiana-Mississippi, and Texas – and the other is California. There are different rice types associated with a production region. California mainly produces short and medium grain; while Arkansas, Texas, and Louisiana primarily produce long and also medium grains. We determine the potential market integration of these rice markets by applying a Vector Error Correction Model and Directed Acyclic Graphs to monthly free on board milled rice price data from August 1986 to December 2015. Results suggest that Arkansas-Missouri region is the leading price reference in the long grain markets. Arkansas-Missouri medium grain also plays an important role in the medium grain markets. California medium grain markets are weakly exogenous in the short run, but affected by Arkansas-Missouri medium grain in the longer term. As anticipated, Arkansas-Missouri long grain milled rice markets are driven by rough rice futures price in the longer term. Interestingly, Arkansas-Missouri medium grain market has a sizable impact on long grain markets even though long and medium grains are not substitutes. This may be due to land competition to long grain rice production in Arkansas, a major area of long grain rice production.