How to serve multiple HTML files with React?

if you are use create react app you must eject your project first because you must change your entry point in Webpack configuration

first eject ( if you do not have webpack config file )

    npm run eject 

and after that go to config file

in webpack.config.js

entry: {
    index: [
      require.resolve('react-dev-utils/webpackHotDevClient'),
      require.resolve('./polyfills'),
      require.resolve('react-error-overlay'),
      paths.appIndexJs,
    ],
    admin:[
      require.resolve('react-dev-utils/webpackHotDevClient'),
      require.resolve('./polyfills'),
      require.resolve('react-error-overlay'),
      paths.appSrc + "/admin.js",
      ]
  },
  output: {
    path: paths.appBuild,
    pathinfo: true,
    filename: 'static/js/[name].bundle.js',
    chunkFilename: 'static/js/[name].chunk.js',
    publicPath: publicPath,
    devtoolModuleFilenameTemplate: info =>
      path.resolve(info.absoluteResourcePath),
  },

after that you should add Wepack plugin and added that to your project

 new HtmlWebpackPlugin({
      inject: true,
      chunks: ["index"],
      template: paths.appHtml,
    }),
    new HtmlWebpackPlugin({
      inject: true,
      chunks: ["admin"],
      template: paths.appHtml,
      filename: 'admin.html',
    }),

also you should rewrite urls

historyApiFallback: {
      disableDotRule: true,
      // 指明哪些路径映射到哪个html
      rewrites: [
        { from: /^\/admin.html/, to: '/build/admin.html' },
      ]
    }

you can read this page for more informations http://imshuai.com/create-react-app-multiple-entry-points/