Question: When was the County that is home to the California city of Walnut creek, which itself has a population of 1,052,700, established?
Options:
2010-07-01
1996-09-07
-4000000
2007-12-01
2014-05-08
1698-01-01
1978-01-20
1970-05-06
1821-01-01
1946