index.js

// src/index.js
import React from 'react';
import ReactDOM from 'react-dom';
import { browserHistory } from 'react-router';

import Routes from './routes';

import './index.css';

ReactDOM.render(
  <Routes history={browserHistory} />,
  document.getElementById('root')
);

With react-router-dom

import React from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter } from 'react-router-dom'
import Routes from './routes';

import './index.css';

ReactDOM.render(
  <BrowserRouter>
    <Routes />
  </BrowserRouter>,
  document.getElementById('root')
);

Guide for migration