*Portland, ME: scale issue. Though Portland's place boundary contains an island and some sea area, making it very wonky, this isn't an issue.
*San Juan Capistrano, CA: Just 2 locations (1 singleton and 1 multiton) and no hull. Note that we might want to omit this place.
We might also want to check Twin Cities. Here's the results:
place statecode Issue Reason
Champaign IL No Urbana isn't in the data
Phoenix AZ No Mesa isn't in the data
'''San Francisco''' CA No Twinned with Oakland!
'''Oakland''' CA No Twinned with SF!
'''Stamford''' CT Yes Norwalk
'''Norwalk''' CT Yes Stamford
New Haven CT No Bridgeport isn't in the data
Tampa FL No St. Petersburg
Portland ME No South Portland isn't in the data
'''Minneapolis''' MN Yes St. Paul
'''Bloomington''' MN No Normal isn't in the data
'''Durham''' NC Yes? Raleigh
'''Raleigh''' NC Yes? Durham
Portland OR No Vancouver isn't in the data
Bethlehem PA No Allentown isn't in the data
'''Dallas''' TX Yes? Fort Worth
'''Fort Worth''' TX Yes? Dallas
Seattle WA No Tacoma isn't in the data
A visual inspection suggests that Stamford and Norwalk might be better combined but don't really matter. Minneapolis and St. Paul are pretty separate and really separate after removing outliers. Rarleigh and Durham are completely separate (Cary is more of an issue), as are Dallas and Fort Worth and SF and Oakland.
===First Estimation(s)===