Which different parts of the United States does Martin Luther King mention in his speech?

I will assume you are referring to Dr. Martin Luther King, Jr.'s famous "I have a dream" speech, delivered in 1963 from the steps of the Lincoln Memorial in Washington, DC as part of the March on Washington. In his speech, King references various locations in the United States, both general and specific. He mentions "motels of the highways and the hotels of the cities" where African Americans are not allowed to stay, and that their mobility has been merely "from a smaller ghetto to a Larger one". Specific areas he mentions are Mississippi, Alabama, South Carolina, Georgia and Louisiana--the South, where prejudice is still acceptable and a daily occurrence. At the end, he speaks of freedom ringing from all parts of the country:

...from prodigious hilltops of New Hampshire. Let freedom ring from the mighty mountains of New York. Let freedom ring from the heightening Alleghenies of Pennsylvania. Let freedom ring from the snowcapped Rockies of Colorado. Let freedom ring from the curvaceous slopes of California. But not only that. Let freedom ring from Stone Mountain of Georgia. Let freedom ring from Lookout Mountain of Tennessee. Let freedom ring from every hill and molehill of Mississippi...

When this happens, King says, then we will truly be free at last.