A simple data aggregation in R with dplyr produced attendee aggregate counts per state. From there I moved over to CartoDB and uploaded the data for the next, often dreaded task, geocoding.
After only a couple of missteps, the geocoding at the state level was completed. A couple clicks produced a choropleth map, a suitable color scheme, and labels to show the number of attendees per state. The last task was to make the location of ODSC East, the Boston Convention and Exhibition Center, stand out.
After getting the coordinates of the venue from Google Maps, some more poking around put it front and center in CartoDB. You can see the resulting map here.