Clark's diary is a four-by-six inch bound book. The printed title page describes it as “Ward's ‘Line a Day’ Book, A comparative record for five years” (copyright 1892). The ‘comparative’ format is unusual: each page is printed with a month and date, and is divided horizontally into five sections; the diarist fills in the events of each date five years in a row, resulting in a unique retrospective view. In order to fit so many entries on each small page, each entry is allotted only four short lines.
Clark wrote her name and address in the front of the diary. Entries began with January, 1906 and ended with December 31, 1910, although the first several weeks of 1906 were blank or incomplete and there are a few other blank dates. A few entries and end-of -year reflections continue into the ‘memoranda’ section at the end of the diary. Over the years, Clark wrote in several colors of ink and pencil. Clark's handwriting is hard to read, and when she referred to critical pints in her romances she resorted to cryptic notes, exclamation points and dashes. Entries made during the last year of the diary, 1910, were even briefer than usual, and Clark's handwriting became even less legible.