Causal message logging spread recovery information around the network in which the processes execute. This is an attractive property for wide area networks: it can be used to replicate processes that are otherwise inaccessible due to network partitions. However, current causal message logging protocols do not scale to thousands of processes. We describe the Hierarchical Causal Logging Protocol (HCML) that is scalable. It uses a hierarchy of proxies to reduce the amount of information a process needs to maintain. Proxies also act as caches for recovery information and reduce the overall message overhead by as much as 50%. HCML also leverages differences in bandwidth between processes that reduces overall message latency by as much as 97%.