Midstream assets, specifically pipelines and processing centers, play a crucial role in America's energy future. The industry is growing rapidly and may play a crucial role in the future of your portfolio. There are many companies to keep an eye on, and it's an industry worth watching. Here's a recap of this week's highlights and lowlights.

New kid on the block
EQT Midstream Partners (NYSE: EQM) went public on Tuesday. It was the first U.S. market IPO since Facebook "excitement" more than a month ago. EQT Midstream operates natural gas pipelines and storage systems in the Appalachian Basin, which includes the Marcellus shale play. Its parent company, EQT (NYSE: EQT), is one of the biggest gas producers in the region.

EQT Midstream's growth will depend in part on its ability to secure customers in the Marcellus. Its parent company accounted for 65% of its volumes in the first quarter, but nepotism will only get you so far. Luckily for EQM, dry gas production in the Northeast is expected to more or less double over the next 20 years.

The company sold 12.5 million common units priced at $21, raising just over $262 million. Shares rose 14% in their first day of trading.

1 out of 3 ain't bad
TransCanada (NYSE: TRP) finally got some good news regarding its Keystone XL pipeline. The Army Corps of Engineers issued one of three permits necessary to build the southern section of the XL. You read that right, one-third of the required permits for one section of the pipeline -- that is how you spell success at TransCanada now.

The southern leg of the Keystone XL will carry crude from Cushing, Okla., to Texas refineries on the Gulf Coast. This section's capacity is 830,000 barrels per day. It will cost $2.3 billion to build and construction is slated to begin this summer, provided TransCanada obtains the other two permits.

Foolish takeaway
Midstream is where it's at, folks. The energy industry will spend an estimated $130 billion to $210 billion expanding natural gas infrastructure over the next 20 years. After all, the more oil and gas that flows through those pipelines and processing centers, the more cash there is to flow into your pockets. Stay on top of all the midstream action by adding the companies above to My Watchlist.