Customers in the AWS GovCloud (US-West) Region can now use AWS Secrets Manager to manage secrets such as database passwords and API keys needed to access their applications, services, and IT resources.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/06/AWS-Secrets-Manager-is-now-available-in-the-AWS-GovCloud-US-West-region/