JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrap">
<div id="container">
    <div id="landingpage">
        <p>Landing Page</p>
    </div>
    <div id="galone" class="vert"></div>
    <div id="galtwo" class="vert"></div>
    <div id="galthree" class="vert"></div>
    <div id="galfour" class="vert"></div>
    <div id="galfive" class="vert"></div>
    <div id="galsix" class="vert"></div>
</div>
</div>

CSS

#wrap {
    width: 100%;
    height: 100%;
    overflow-x: hidden;
    overflow-y: hidden;
}

#container {
    position: relative;
    height: 200px;
    width: 1000px;
}
#landingpage {
    height: 200px;
    width: 400px;
    background-color:blue;
    position: relative;
    float: left;
}
#galone {
    height: 200px;
    width: 100px;
    background-color: green;
    position: relative;
    float: left;
}
#galtwo {
    height: 200px;
    width: 100px;
    background-color: brown;
    position: relative;
    float: left;
}
#galthree {
    height: 200px;
    width: 100px;
    background-color: pink;
    position: relative;
    float: left;
}
#galfour {
    height: 200px;
    width: 100px;
    background-color: orange;
    position: relative;
    float: left;
}
#galfive {
    height: 200px;
    width: 100px;
    background-color: purple;
    position: relative;
    float: left;
}
#galsix {
    height: 200px;
    width: 100px;
    background-color:lightgreen;
    position: relative;
    float: left;
}
p {
    margin-top: 90px;
}

JavaScript

var scroller = {};
scroller.e = document.getElementById("wrap");

if (scroller.e.addEventListener) {
    scroller.e.addEventListener("mousewheel", MouseWheelHandler, false);
    scroller.e.addEventListener("DOMMouseScroll", MouseWheelHandler, false);
} else scroller.e.attachEvent("onmousewheel", MouseWheelHandler);

function MouseWheelHandler(e) {
    console.log('scroll');

    // cross-browser wheel delta
    var e = window.event || e;
    var delta = - 20 * (Math.max(-1, Math.min(1, (e.wheelDelta || -e.detail))));

    var pst = $('#wrap').scrollLeft() + delta;

    if (pst < 0) {
        pst = 0;
    } else if (pst > $('#container').width()) {
        pst = $('#container').width();
    }

    $('#wrap').scrollLeft(pst);

    return false;
}