Hi use this below URL for one column but displaying multiple columns
http://jsfiddle.net/alforno/g4stL/
 $("#search").mcautocomplete({
 showHeader: true,
columns: [{
    name: 'City',
    width: '150px',
    valueField: 'name'
}, {
    name: 'State',
    width: '120px',
    valueField: 'adminName1'
}, {
    name: 'Country',
    width: '120px',
    valueField: 'countryName'  }],
    select: function (event, ui) {
    this.value = (ui.item ? ui.item.name : '');
    return false;
    },
minLength: 1,
source: function (request, response) {
    $.ajax({
        url: 'http://ws.geonames.org/searchJSON',
        dataType: 'jsonp',
        data: {
            featureClass: 'P',
            style: 'full',
            maxRows: 12,
            name_startsWith: request.term,
            username: "demo"
        },
        // The success event handler will display "No match found" if no items are returned.
        success: function (data) {
            var result;
            if (!data || data.length === 0 || !data.geonames || data.geonames.length === 0) {
                result = [{
                    label: 'No match found.'
                }];
            } else {
                result = data.geonames;
            }
            response(result);
        }
    });
} });