It was quickly followed by gold in the men 's 4x100 medley relay , which was Michael Phelps ' final race .
The women 's medley relay marked the United States ' 23rd gold in Rio .
United States was quickly followed by gold in the men 's 4x100 medley relay , which was Michael Phelps ' final race .
The women 's medley relay marked the United States ' 23rd gold in Rio .