The above map shows the difference between the county boundaries in 1840 (black lines) and the modern-day boundaries (white lines). In this enumeration, the southern portion of modern-day Mason County is included in the Menard Co boundaries, while the southeast corner of Menard County is enumerated with Sangamon County. A person listed in this census as being in Menard Co may have actually resided in modern-day Mason Co, or someone that actually lived in southern Menard Co would be found in the Sangamon Co census. No township or precinct names were given in this enumeration.
The 1840 federal census only gives the names of the head of household, names of the family members were not given until the 1850 census.
Please note that many of the proper names were abbreviated in the original census, and I have transcribed them as such. Thomas is often written as Thos., James is written as Jas., and so on. Click here to see more abbreviations and the proper names they represent, as well as samples of the handwriting used in the 1840 census.