There are ten series that divide the Lahti Family Collection. Series I contains both paper and electronic documents pertaining to genealogical history, some family ephemera, as well as Local historical information such as photographs and news articles about Northern Illinois University and DeKalb.

Ric Lahti’s manuscripts makes up Series II; it is divided into four sub-series. Sub-series A contains personal records and ephemera, while sub-series B contains financial material unrelated to family businesses. Account ledgers from both businesses are included in the series.

Series III contains both paper and electronic documents consisting of materials from Alice Margaret Hitchcock Lahti including scrapbooks and memory books from her school days at McMurry School.

Material from Jennye Lahti Fry make up Series IV. Included in this series are photo albums created by Jennye Lahti. An index to each photo album is provided in the folders containing the albums. Also included in this series are photographs and documents pertaining to Jennye’s husband, specifically his involvement with work with various agricultural companies and a photograph of himself on a basketball team.

Rachel Lahti Donnelly material make up Series V. This material includes groups Rachel Lahti Donnelly participated in including The Stagecoach Players.

Fraternal Organization material make up Series VI. This series contains information concerning the fraternal organizations in which "Ric" Lahti participated: Shriners and Masons, as well as material from Alice and Rachel’s participation in Job’s Daughters, an organization associated with the Shriners.

Correspondence comprises Series VII.

Series VIII contains information about the golfing careers of Ric and Alice Lahti. Much of the material relates to Ric Lahti’s time at the Kishwaukee Country Club, but documents from other clubs and tournament in which he participated are also included. Alice Lahti’s golfing career is highlighted.

Series IX contains more detailed information about the Lahti businesses. Sub-series A holds information about the Lahti Clothing Store of Sycamore. Included in this series is the history of the clothing store, information on the owners of the store before and after Ric Lahti, business and financial records, employee information, and promotional materials. Sub-series B focuses on other Lahti records, and includes ledgers from Ric’s Restaurant in Belvedere, as well as documents on Ric Lahti’s employment elsewhere.

The Lahti family’s private life and Finnish ties are located in Series X. Many of the correspondences that are contained in this series are written in Finnish to Jennye Lahti, Ric Lahti’s sister. Also in this series is funeral information from Matti and Sofia Lahti, parents of Ric.