MPLX (NYSE: MPLX) has undergone an important transformation over its six years as a public company. It has gone from an entity that mainly owned logistics assets serving its oil-refining parent Marathon Petroleum (NYSE: MPC) to a company that operates across the midstream sector. As a result, it's starting to capture an increasing amount of the estimated $800 billion of investments needed to expand North America's energy infrastructure footprint in the coming years.Those expansion projects position MPLX to continue growing its distribution to investors, which it has done in each of the 22 quarters since it came public.