You can say it both ways and both would mean essentially the same thing. If we want to be really grammatically technical, as a native English speaker, if we envision a 'location' as a setting of something in the world, then if you say 'the location of the company is California' then it means the company is in California. However, if you say 'the location of the company is IN California' then it seems to refer to a specific section of California in which the company is located. This is to say that the sentence with 'in' is potentially more specific than the first in terms of the geographical location. HOWEVER, because of the non-specific nature of the sentence, the sentences are essentially identical. In both sentences we know that the company is somewhere in California but not exactly where, even though there speaker of the sentence might know more specific details when he says 'in' rather than when he omits the preposition. Still, I would say the vast majority of people don't think about such intricate details as this ever!

Thank you ^^

I'm not sure, hence a comment rather than an answer. I think that both are possible, but I think that normally if you said 'location of', you would say something more specific than a state.