Before J.P. Dondero Genealogy had it's own blog I did a fair amount of posting on my personal blog "Jennifer's Genealogy (a)Musings." Some posts are related to my personal research but some are similar to this blog. Below is a post from 2010 I think provides some (still) relevant information.
Earlier this month Dick Eastman wrote an article about the Newberry Library's completion of the Digital Atlas of Historical County Boundaries. You can read that article here. One of the options offered to users of the Digital Atlas is downloading KMZ files for use with Google Earth. I went straight to this option for Georgia and proceeded to loose several hours I was supposed to spend on other work! I've shared some of the mapping I've done in Google Earth using great historic maps available for Georgia but the Digital Atlas really takes this to another level (check out two of my favorite examples here and here or try the label "Mapping Mondays").
In Google Earth it's really hard to determine if Georgia Land Lottery map overlays are aligned properly for the land lots. There are a number of different historic maps available and the results will be slightly different for each. Also, I have noticed inconsistencies in some counties between the Digital Atlas county outlines and some of the historic maps I've used. Should this cause an issue for an area of interest, the Historical Atlas of Georgia Counties includes both descriptions and maps. This provides the possibility of determining the correct county for an area in question.
Using the Digital Atlas has really opened my eyes to exactly how the counties changed and when. There are certain time periods (such as the 1830s and 1850s) I am very familiar with one county's creation/changes and didn't realize I was making assumptions about a neighboring county of interest. Seeing the boundaries change (year by year, as opposed to decade by decade with historical census maps) made me aware of this and made me realize there are some counties I should check for records during certain time periods.
I can't speak for other states or even for the headright areas of Georgia but there are so many maps available for the Land Lottery counties in Georgia that tracing any land owned is a vital step, especially if you're stumped. Combining the Digital Atlas with historical maps, Google Earth, and traditional deed searching can really simplify the process of locating your ancestors. What used to be extremely time consuming and problematic is getting faster and simpler. Instead of resorting to checking "all the surrounding counties" as used to be necessary, you can identify the most likely county (or counties) and time period to search for additional records. You may still end up searching all the surrounding counties but why not give yourself the best chance at success, first.
Oh, and did I mention all of these resources are free?
Links to great resources for Georgia land lot mapping:
Digital Atlas of Historical County Boundaries
Historical Atlas of George Counties
District Plats of Survey (Georgia's Virtual Vault)
Georgia County Maps (Georgia's Virtual Vault)