Genetic relationships among languages can provide considerable insight into the culture, migrations, and contacts of human populations. However, it has so far been difficult to find and compare hypotheses about genetic relationships, since they exist only in scholarly books and papers, and can only be accessed individually. The Multi-tree project will develop a digital library of scholarly hypotheses about language relationships, one which is fully documented and transparently traceable to the scholarly work upon which it is based. Hypotheses about groups of related languages will be displayed graphically as familiar diagrams of family trees, with each node opening to display additional information on the language or subgrouping represented. Moreover, competing hypotheses about the same language family will be displayed as two or more trees aligned side by side for easy comparison. The Multi-Tree database will also be integrated with the existing LINGUIST List databases, which house a wealth of information about language and linguistics collected over a 15-year period of building electronic infrastructure for the discipline. The Multi-Tree project thus has considerable potential to contribute to research and education both within the field of linguistics and in related scientific disciplines. The project will provide accessible data and an overview of language classification which can trigger new hypotheses. It will make relationships between lesser-known languages better known, stimulating research on minority languages. Finally, the online search facility will constitute a captivating instructional tool, for use in K-12 through graduate education.