We use the German Crisis of 1931, one of the largest bank runs in financial history, to study how depositors behave in the absence of deposit insurance. We find that banks lose on average around 25% of their overall deposit funding during the run and that there is an equal outflow of retail and non-financial wholesale deposits from both ex-post failing and surviving banks. This implies that regular depositors are unable to identify failing banks. In contrast, the interbank market precisely identifies which banks will fail: the interbank market collapses for failing banks entirely but it continues to function for surviving banks, which can borrow from other banks in response to deposit outflows. We argue that since regular depositors appear uninformed it is unlikely that deposit insurance would exacerbate moral hazard. Instead, interbank depositors are best positioned for providing “discipline” via short-term funding.