Table: congress_successors
Columns: district
vacator
reason_for_change
successor
date_successor_seated

Question: What is the reason for change when maryland 6th is the district? 
SQL: SELECT "reason_for_change" FROM congress_successors WHERE "district" = 'Maryland 6th'

Question: Who is the vacator when south carolina 4th is the district?
SQL: SELECT "vacator" FROM congress_successors WHERE "district" = 'South Carolina 4th'

Question: Who is the successor when florida territory at-large is the district?
SQL: SELECT "successor" FROM congress_successors WHERE "district" = 'Florida Territory At-large'