How did the baha'i faith spread?

Answer 1

In it's short 164 year history the Baha'i Faith is the second most wide spread religion next to Christianity. The Baha'i Faith though has not been divided into sects or schisms. there is only one Baha'i Faith no matter where in the world you travel.

ANSWER 2:

As of 2012 (168-year history), the Baha'i Faith is comprised of more than 2,100 ethnic and tribal groups residing in more than 230 countries and territories.

Answer 2

The Baha'i Faith has and continues to spread through the guidance of the Head of the Faith. This was first Baha'u'llah who asked certain of His followers to go to certain places and see if people there might be interested. He appointed His son, 'Abdu'l-Baha to succeed Him and He continued this practice, even writing lists of places where Baha'is should go.

Today it is the Universal House of Justice, the international governing council, which coordinates this effort. As a result, in a century and a half the Baha'i Faith has become the second most widespread religion on the planet.

This is all done with no clergy and no missionaries. Individual Baha'is or families go to a new place, get a job, make friends and seek to find people who might be interested. Baha'is have a spiritual obligation to not speak about their faith if the person is not interested.