I have an older MacBook Pro (Mid 2009) that cannot start and need to reinstall OS X from USB key or disc. With another MacBook I tried to download OS X El Capitan but is not available, only macOS Sierra, but my laptop is too old for macOS Sierra. How can download OS X El Capitan or older version of OS X?
You can download OS X El Capitan 10.11.6 (6.21 GB) via this link, which will open first in the Browser, then in the App Store.app.
OS X El Capitan
This version of OS X El Capitan is for users running OS X Snow Leopard who would like to upgrade to macOS Sierra. If you are running Snow Leopard and would like to upgrade to Sierra, you need to install El Capitan first. This version of El Capitan can also be installed on Mac computers that are not comparable with Sierra.