Note, in newer versions of the router, this won't work because a route can only contain one child. Try wrapping the two routes in a <switch>:</switch>

  <Switch>
    <Route exact path="/" component={ List } />
    <Route path="/react" component={Detail}  />
  </Switch>

In newer versions of React, this won't work without a history prop and hashHistory. Depending on how you import hashHistory, the code will look something like this:

let hashHistory = createHashHistory();

<Router history={hashHistory}>
    <Route path="/" component={ Detail } />
</Router>,