I'm a rails novice, but I'm a sucker for the least pain approach.
This is borderline - for an initial data load this small I would still be tempted to do the Excel voodoo.
This information is generally static (apart from major world wars and collapse of national governments), so the tables should be pretty static. If this particular table (or table set) is dynamic enough to require a migration (i.e. columns will change), I would be tempted to look at my designs again for a flaw in the data model.
The tool that I would use for an ongoing migration effort or something really sizeable is not publicly available :o( but most RDBMS's come with fast unload and load utilities that can handle this sort of task, provided the data structure does not change much.
Finally, I can actually mount comma delimited files as external tables in the RDBMS that I prefer for rails projects, so my initial import might be to look up how to mount the external table, then "select * from oldtable into newtable", or "insert into newtable (col1, col1, ...) select (col1, col2, ...) from oldtable", depending on the exact requirements of the new table.
I know that this isn't exactly what you are looking for, but I hope it helps.