For the first time since mid-April, American drivers are seeing a number below four on the pump. The national average retail gasoline price hit $3.997 per gallon on June 15, according to GasBuddy data, slipping just barely under a threshold that had become a stubborn ceiling since the Iran conflict rattled global energy markets.

How we got here

The backdrop to this price drop is a geopolitical one. Oil prices fell more than $4 per barrel in recent sessions as markets grew optimistic about a possible preliminary agreement between the US and Iran. The core hope: that a deal could facilitate reopening the Strait of Hormuz, the narrow waterway responsible for roughly one-fifth of global oil trade.

When the strait was effectively closed earlier this year due to escalating tensions, it choked a critical artery for international energy flows. Tanker traffic disruptions sent crude prices surging and dragged gasoline along for the ride. By late March, the national average had climbed to $4.02 per gallon.

Current gasoline prices remain approximately 90 cents per gallon higher than they were at this time last year. For a household filling a 15-gallon tank once a week, that translates to roughly $700 in additional annual fuel costs compared to twelve months ago.