User gets 5 answers correct regardless of input -- anyone know why?

var correct = 0;
var question1 = prompt('What is the capital of Wyoming?');
if (question1.toUpperCase() ===  "CHEYENNE") {
  correct += 1;
}
var question2 = prompt('What is the capital of Pennsylvania?');
if (question2.toUpperCase() ===  "HARRISBURG") {
  correct += 1;
}
var question3 = prompt('What is the capital of Oregon?');
if (question3.toUpperCase() ===  "SALEM") {
  correct += 1;
}
var question4 = prompt('What is the capital of Kentucky?');
if (question4.toUpperCase() ===  "FRANKFORT") {
  correct += 1;
}
var question5 = prompt('What is the capital of West Virginia?');
if (question5.toUpperCase() ===  "CHARLESTON") {
  correct += 1;
}


if ( correct = 5) {
  document.write('You got ' + correct + ' answers correct! Hooray for useless knowledge!');
    } else if ( correct >= 3 ) {
  document.write('You got ' + correct + ' answers correct! You might be smarter than a 5th grader.');
    } else if ( correct >= 1) {
  document.write('You only got ' + correct + ' answers. Whatever, no one cares about these places anyways.');
    } else {
  document.write('You need to go back to 5th grade.');
    }