The U.S. manufacturing backlog accelerated for the third straight month in September, with the Institute for Supply Management's Backlog of Orders Index climbing 4.6 percentage points to 56.4% — a signal that factory order books are stacking up faster than shippers can move them.

ISM's headline Manufacturing PMI registered 54.5% in September, the ninth consecutive month of expansion but 0.1 percentage points below August's reading. S&P Global's parallel gauge rose two points to 55.9, reinforcing the picture of an industrial sector still pulling volumes through North American freight networks.

What does the supplier-deliveries slowdown mean for carriers?

ISM's Supplier Deliveries Index read 59% in September, marking the tenth consecutive month in which factories reported slower delivery performance. Anything above 50% in this subcomponent means inputs are taking longer to arrive, and that is a freight-positive signal for truckload, intermodal and less-than-truckload operators running lanes into the industrial Midwest and Southeast.

Five of the six largest U.S. manufacturing industries expanded during the month — computer and electronic products; food, beverage and tobacco products; transportation equipment; machinery; and chemical products. That breadth translates into wider freight demand than a narrow uptick would.

The New Orders Index reached 55.3%, up 1.6 percentage points from August and in expansion for a ninth straight month after four contractions. The Production Index eased 1.6 points to 56.7%, suggesting factories are taking in orders faster than they are shipping finished goods.

Why is the prices index at 77.9%?

ISM's Prices Index jumped 6.8 percentage points to 77.9% from August's 71.1%, the steepest single-month acceleration of 2026. Susan Spence, chair of ISM's Manufacturing Business Survey Committee, said the surge has renewed her concern about price volatility.

"The most recent surge in price growth has renewed my concern about price volatility," Spence said on a Thursday media call. "Trade wars, chaos, whatever you care to call it, is really what's affecting inflation."

For freight buyers, a 77.9% reading has historically correlated with rising spot rates on dry van and reefer lanes out of Texas, Illinois and California, as producers compete for capacity to clear material into and out of plants.

How are the cross-border lanes holding up?

The New Export Orders Index lost 2.3 percentage points to 50.9%, the weakest reading since the spring. The Imports Index slipped 1.5 points to 51%. Respondents linked the softness to U.S. tariffs on Canada and Ottawa's retaliatory duties on U.S. steel and aluminum, a friction reshaping truckload flows across the Detroit–Windsor and Buffalo–Fort Erie corridors.

"Sentiment is certainly worrisome," especially around the Canada tariffs, Spence said.

One machinery respondent quantified the impact: "Orders have doubled yet again, and delivery times have also doubled, in the semiconductor, electronics and government sectors … Canada tariffs have impacted cross-border costs and left our supply chain team scrambling — those supply chains took years to develop and nurture."

What does the labor gauge show?

The Employment Index rose 1.5 percentage points to 52.7%, consistent with the 16,000 manufacturing jobs the Bureau of Labor Statistics reported for August. Spence noted the figure has bounced up and down since June rather than trending in a single direction.

Customers' Inventories fell 1.2 points to 41.6%, staying in what ISM calls "too low" territory. Historically, lean customer stocks translate into restocking freight in the following two to four months, supporting inbound volumes for box truck and LTL carriers serving distribution centers.

What's the forward read?

Spence said 60% of September's survey comments carried a negative tone, with pricing volatility flagged by 46% of respondents, tariffs by 34%, the Iran war by 30% and longer lead times by 21%.

With the backlog climbing, prices accelerating and supplier deliveries still slowing, freight capacity on industrial lanes is likely to remain tight into the fourth quarter, and carriers with reefer, flatbed and intermodal assets positioned near the U.S.–Canada border will be closely watching whether October's data confirms or cools the pressure.