Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_39 ( floors INTEGER, name VARCHAR, year VARCHAR )

### Question ###
Name of 900 north michigan, and a Year smaller than 1989 involves what lowest floors?

### Accurate SQL ###

SELECT MIN(floors) FROM table_name_39 WHERE name = "900 north michigan" AND year < 1989