is this legal? i was a manager and i was fired for no reason but told the owner the day before i was pregnant.

It is NOT legal to terminate an employee because she is pregnant.  The federal statute against pregnancy discrimination only applies to employers who have approximately 40 employees.  But, it would still be considered gender discrimination under federal law if there are at least 15 employees. There may also be state statutes that specifically apply to pregnancy discrimination and would apply even with fewer than 40 employees.  Your employer will need a very strong explanation for why he terminated you given the timing of the discharge from when you informed them of being pregnant. See an attorney who specializes in this area immediately