CSS display: inline-block drops to next line

Question

I have a simple grid that I am testing out.

I decided to change something from float: left to display: inline-block in the attribute select

Answer 1

<div class='header'>
        <h1>China</h1>
    </div>
    <div class='row'>
        <div class='col-3'>
            <ul>
                <li>The Flight</li>
                <li>The City</li>
                <li>The Island</li>
                <li>The Food</li>
            </ul>
        </div><!--
        --><div class='col-9'>
            <h1>The City</h1>
            <p>Chania is the capital of the Chania region on the island of Crete. The city can be divided in two parts, the old town and the modern city.</p>
            <p>Resize the browser window to see how the content respond to the resizing.</p>
        </div>
    </div>

small hack, try these <!-- --> it ignores the whitespace

EDIT: and if you want to remove the tiny gap to your header:

.col-9 {
  vertical-align: top;
}

demo

Answer 2

@Thielicious's answer has a fine solution. Here's the explanation, and the answer to your

I am wondering why when using float: left there is enough space for col-9 and everything works fine but, when using display: inline-block the element drops down to the next line.

Whitespace between inline-block elements takes up space on the rendered page.

Chris Coyier gives a run down of different ways to get around this (includes the method of html comments, as in Thielicious's answer, as well as some other HTML tricks and CSS methods)