A log book of geyser activity is kept by park rangers and volunteers at the Old Faithful Visitor Center. The activity reported in this log mainly concerns the Upper, Midway and Lower Geyser Basins but other areas infrequently are included.

Lynn Stephens has undertaken the monumental task of transcribing the handwritten log books onto the computer.

As common courtesy, if you use the data here, you should reference the log book as your source and include thanks to all of those that have contributed to it.