In the settings tab you are allowed to change the home page URL. However this will break your wordpress site. It auto redirect both the front and back end pages. You can not log back and and fix it. You must go into your MySQL database and change the table field. You must go to the wp_options table and then the siteurl field and change it back.
Also on a side note if you want to make a sub page your blog page and not the home page you can also do this in the settings. Go to the reading tab and then create a page, it will be blank, then select it the post page field.