First, you have locate a girl from the west coast and a girl from the east coast. Then, you have to find a solid gold dildo. Once you've aquired the solid gold dildo, you give it to the girls, who proceed to use it. This unites the west coast and east coast with a gold spike. Grant would be proud.
"President Grant, we've completed the Transcontinental Railroad."
"Marvelous! When can I ride it?"
"Hmm... I believe that's up to them sir."