How can I force div contents to stay in one line with HTML and CSS?

I have a long text inside a div with defined width:

HTML:

<div>Stack Overflow is the BEST!!!</div>

CSS:

div {
    border: 1px solid black;
    width: 70px;
}

How could I force the string to stay in one line (i.e., to be cut in the middle of “Overflow”)?

I tried to use overflow: hidden, but it didn’t help.