This Article introduces the Jurist-Derived Judicial Ideology Scores (JuDJIS), an expert-sourced measure of judicial traits that can locate nearly every Article III judge on a single scale. The measure derives from the text of over ten-thousand written evaluations by a representative sample of thousands of jurists, conducted over three decades and ongoing. The resulting data are interval-level, dynamic, and potentially multi-dimensional. Validation using thousands of appellate decisions indicates that the JuDJIS ideology estimates predict outcomes substantially more accurately than existing appellate ideology measures, including the Judicial Common Space. Using the data, this Article finds evidence of judicial depolarization over time, and explores presidents’ relative success in pushing the judiciary toward their preferred ideology. These pilot studies show how the data sets could open numerous avenues of research in judicial politics that were previously closed due to data limitations.